Exception (9): epc1=0x4020f694 epc2=0x00000000 epc3=0x00000000 excvaddr=0x0000032d depc=0x00000000

I'm using NodeMCU and every couple of minutes I'm getting this issue: After troubleshooting, I find out that these functions are the reason but I don't why

void humidity() {
    delay(2000);
    float h = dht.readHumidity();
    float t = dht.readTemperature();
    Serial.print("Hum:   ");
    Serial.println(h);
    Serial.print("Temp:   ");
    Serial.println(t);

    if (isnan(h) || isnan(t)) {
    Serial.println("Failed to read from DHT sensor!");
    Firebase.setInt (link+"/HUMIDITY",0);
    Firebase.setInt (link+"/TEMPERATURE",0);}
    else{
    Firebase.setInt (link+"/HUMIDITY",h);
    Firebase.setInt (link+"/TEMPERATURE",t); }

    valuefunc();
    if(h>setvalue){pin();}
    else {revpin();}  
    if(t>setvalue){pin();}
    else{revpin();}  
}

void ultrasonic(){
    digitalWrite(trigPin, LOW);
    delayMicroseconds(2);
    digitalWrite(trigPin, HIGH);
    delayMicroseconds(10);
    digitalWrite(trigPin, LOW);
    long duration = pulseIn(echoPin, HIGH);
    float distance= duration*0.034/2;
    Serial.print("Distance: ");
    Serial.println(distance);
    Firebase.setInt (link+"/ULTRASONIC",distance);

    valuefunc();
    if(distance>setvalue){pin();}
    else{revpin();} 

}

void ir(){
         if(digitalRead(irpin)==HIGH){Firebase.setString(link+"/IR","ON");Serial.println("IR: ON");}
    else if(digitalRead(irpin)==LOW) {Firebase.setString(link+"/IR","OFF"); Serial.println("IR: OFF");}

    setvalueir=Firebase.getString(link+"/VALUEIR");
    Serial.print("VALUEIR: ");
    Serial.println(setvalueir);

    if(((setvalueir=="ON") && (digitalRead(irpin)==HIGH)) || ((setvalueir=="OFF") && (digitalRead(irpin)==LOW))){pin();}
    if(((setvalueir=="ON") && (digitalRead(irpin)==LOW)) || ((setvalueir=="OFF") && (digitalRead(irpin)==HIGH))){revpin();}  
}

void analog(){
    float analog = analogRead(A0);
    Serial.print("Analog Value:");
    Serial.println(analog);
    Firebase.setInt (link+"/LDR",analog);

    valuefunc();
    if(analog>setvalue){pin();}
    else{revpin();}  
    delay(1000);
}

void analog1(){
    float analog1 = analogRead(A0);
    Serial.print("Analog 1:");
    Serial.println(analog1);
    Firebase.setInt (link+"/WATER",analog1);

    valuefunc();
    if(analog1>setvalue){pin();}
    else{revpin();}  
    delay(1000); 
}

void analog2(){
    float analog2 = analogRead(A0);
    Serial.print("Analog 2:");
    Serial.println(analog2);
    Firebase.setInt (link+"/SOIL",analog2);

    valuefunc();
    if(analog2>setvalue){pin();}
    else{revpin();}  
    delay(1000);
}

void pin(){
    Pin1=Firebase.getString(link+"/PIN1");
    Pin2=Firebase.getString(link+"/PIN2");

    if(Pin1=="HIGH"){digitalWrite(Digi1,HIGH);}
    else{digitalWrite(Digi1,LOW);}
    if(Pin2=="HIGH"){digitalWrite(Digi2,HIGH);}
    else{digitalWrite(Digi2,LOW);}
}

void revpin(){  
    Pin1=Firebase.getString(link+"/PIN1");
    Pin2=Firebase.getString(link+"/PIN2");  
    if(Pin1=="HIGH"){digitalWrite(Digi1,LOW);}
    else{digitalWrite(Digi1,HIGH);}
    if(Pin2=="HIGH"){digitalWrite(Digi2,LOW);}
    else{digitalWrite(Digi2,HIGH);}
}

void valuefunc(){
    setvalue=Firebase.getString(link+"/VALUE").toInt();  
}  

And the error in serial monitor is:

Exception (9):
epc1=0x4020f694 epc2=0x00000000 epc3=0x00000000 excvaddr=0x0000032d depc=0x00000000

Stack:

ctx: cont
sp: 3ffffa90 end: 3fffffc0 offset: 01a0
3ffffc30:  00000004 00000006 3fff0af0 402094b4  
3ffffc40:  3ffffc90 3fffff10 3fff0af0 4020a380  
3ffffc50:  3ffeeeb4 3fffff10 3ffffec0 40208cb0  
3ffffc60:  3ffeeeb4 3ffffc90 3ffffc90 402073f0  
3ffffc70:  00000002 3fffff10 3ffffec0 40207460  
3ffffc80:  3ffeeeb4 3fffff10 3ffe8b63 40208b80  
3ffffc90:  48474900 00002200 80000124 4020fc40  
3ffffca0:  3fff3e7e 00000030 3ffffd88 4020b60e  
3ffffcb0:  00000124 00000124 3fff0d94 00000000  
3ffffcc0:  4025c4b4 00000020 3ffffd70 4020b60e  
3ffffcd0:  fcac040d d20e1039 8540be8b 3ffffd88  
3ffffce0:  3fff12c1 4bc6a7f0 07ef9db2 00000000  
3ffffcf0:  00000000 4bc6a7f0 4353f7ce 4020c84b  
3ffffd00:  01860017 00000000 00000005 4020e73c  
3ffffd10:  00000008 00000000 3fff0d94 4022991f  
3ffffd20:  00000000 00000008 3ffffd70 4020b7c0  
3ffffd30:  012aec65 4025c63c 3ffffd70 4020ba70  
3ffffd40:  007a1200 3fcb2387 3ffffd00 00000001  
3ffffd50:  3ffffda8 000002d8 000002d8 401007c8  
3ffffd60:  000053c0 00000000 00000000 01000000  
3ffffd70:  3ffffda8 00000001 3fff0d94 00000001  
3ffffd80:  000000c8 40208314 00000020 40100a88  
3ffffd90:  3fff12c1 00000001 3fff0d1c 4020e90b  
3ffffda0:  00001610 000002c2 000002c2 4020c84b  
3ffffdb0:  01860017 00000000 00000005 4020e73c  
3ffffdc0:  000000c8 00000000 3fff0d94 4022991f  
3ffffdd0:  3fff4c84 3fff0f64 00000001 40209e50  
3ffffde0:  3fff0f00 000e000f 3ffffed0 4021892d  
3ffffdf0:  007a1200 3fcb5f70 3fff0f00 402083c8  
3ffffe00:  3ffffe58 00000000 00000001 40100198  
3ffffe10:  000053c0 00000a78 00000a78 401007c8  
3ffffe20:  3ffffe58 00000000 3fff0d94 3ffef1ec  
3ffffe30:  3fffff20 3fffff40 00000020 40100a53  
3ffffe40:  3fffff20 00000000 3fff0b64 4020b744  
3ffffe50:  00000000 3ffe8b63 3ffffed0 4021892d  
3ffffe60:  3ffe8b63 00000000 00000000 402083c8  
3ffffe70:  00000000 3ffffedc 3fff0af0 402083ea  
3ffffe80:  3fffff20 3fffff40 3fff0af0 40208406  
3ffffe90:  3ffe8c00 3fffff40 3ffffed0 40208cb0  
3ffffea0:  00000008 00000007 00000000 00000002  
3ffffeb0:  3ffffc90 00000000 3fffff1c 8020bafc  
3ffffec0:  4020fbd8 3fff0aec 00000000 3ffef090  
3ffffed0:  3fff1108 4020fb98 3fffff1c 00000000  
3ffffee0:  00000100 3ffef090 3fffff00 4020bd1e  
3ffffef0:  80fe872b 3ffeee9c 3ffef070 4020b580  
3fffff00:  80feee9c 3ffeee9c 3ffef070 40201540  
3fffff10:  48474948 3fffff00 84ffff40 2f544f49  
3fffff20:  324e4950 88000000 00000000 4020b580  
3fffff30:  3fffdad0 3fffff40 00000000 40201a0b  
3fffff40:  3fff0f00 000e000f 80fef0bc 4020afb8  
3fffff50:  4024cf72 3ffef0bc 3ffeeed0 40201c66  
3fffff60:  40240000 00000000 80001388 2f544f00  
3fffff70:  534e4553 8000524f 00000005 40100311  
3fffff80:  3fffdad0 00000000 3ffeeee8 4020488b  
3fffff90:  3fffdad0 00000000 3ffef1ac 401001b9  
3fffffa0:  3fffdad0 00000000 3ffef1ac 4020c90c  
3fffffb0:  feefeffe feefeffe 3ffe8560 40100d15  

 ets Jan  8 2013,rst cause:2, boot mode:(3,6)

load 0x4010f000, len 1392, room 16 
tail 0
chksum 0xd0
csum 0xd0
v3d128e5c
~ld

I was having the same problem, I resolved it by removing the delay when answering the request. previous code:

    url = self.requestline
    print(url)
    messagetosend = bytes('on',"utf")
    self.send_response(200)
    self.send_header('Content-Type', 'text/plain')
    self.send_header('Content-Length', len(messagetosend))
    self.end_headers()
    self.wfile.write(messagetosend)
    time.sleep(5)
    return

server_address_httpd = ('192.168.0.108',8080)
httpd = HTTPServer(server_address_httpd, RequestHandler_httpd)
print('server started')
httpd.serve_forever()'

code after removing delay with perfect request

from http.server import BaseHTTPRequestHandler, HTTPServer
 import time
 class RequestHandler_httpd(BaseHTTPRequestHandler):
  def do_GET(self):
    print('You got this http request')

    url = self.requestline
    print(url)
    messagetosend = bytes('on',"utf")
    self.send_response(200)
    self.send_header('Content-Type', 'text/plain')
    self.send_header('Content-Length', len(messagetosend))
    self.end_headers()
    self.wfile.write(messagetosend)
    return
server_address_httpd = ('192.168.0.108',8080)
httpd = HTTPServer(server_address_httpd, RequestHandler_httpd) 
print('server started')
httpd.serve_forever()