PYQT5 and findchild crash with no useful debug info

I've recently switched over from running my .ui file through the pyuic5 command line tool to importing the .ui file by calling uic.loadUi. I decided to go back through some of the tutorials I'd previously done using the command line converter and see if I can get them working using loadUi.

One of them will crash as soon as I click a button but I don't get any useful debug info.

from PyQt5.QtWidgets import QMainWindow, QApplication, QPushButton, QLabel
from PyQt5 import uic
import sys
from PyQt5.uic.properties import QtGui

class UI(QMainWindow):
    def __init__(self):
        super(UI, self).__init__()

        uic.loadUi('catdog.ui', self)

        self.picture = self.findChild(QLabel, 'picture')

        self.cat = self.findChild(QPushButton, "cat")
        self.cat.clicked.connect(self.show_cat)

        self.dog = self.findChild(QPushButton, "dog")
        self.dog.clicked.connect(self.show_dog)

        self.show()

    def show_dog(self):
        self.picture.setPixmap(QtGui.QPixmap("dog.JPG"))

    def show_cat(self):
        self.picture.setPixmap(QtGui.QPixmap("cat.JPG"))


app = QApplication(sys.argv)
UIWindow = UI()
app.exec_()

I suspect it's something to do with the findChild(QPushButton) but I'm a bit lost.

The console just give me this- Process finished with exit code -1073740791 (0xC0000409)

for reference, here's the .ui XML-

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>491</width>
    <height>391</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QWidget" name="gridLayoutWidget">
    <property name="geometry">
     <rect>
      <x>-1</x>
      <y>-1</y>
      <width>491</width>
      <height>391</height>
     </rect>
    </property>
    <layout class="QGridLayout" name="gridLayout">
     <item row="1" column="1">
      <layout class="QVBoxLayout" name="verticalLayout">
       <item>
        <widget class="QLabel" name="picture">
         <property name="text">
          <string/>
         </property>
         <property name="pixmap">
          <pixmap>cat.JPG</pixmap>
         </property>
         <property name="scaledContents">
          <bool>true</bool>
         </property>
        </widget>
       </item>
       <item>
        <layout class="QVBoxLayout" name="verticalLayout_3"/>
       </item>
       <item>
        <layout class="QHBoxLayout" name="horizontalLayout">
         <item alignment="Qt::AlignTop">
          <widget class="QPushButton" name="cat">
           <property name="font">
            <font>
             <pointsize>16</pointsize>
            </font>
           </property>
           <property name="text">
            <string>Cat</string>
           </property>
          </widget>
         </item>
         <item alignment="Qt::AlignTop">
          <widget class="QPushButton" name="dog">
           <property name="font">
            <font>
             <pointsize>16</pointsize>
            </font>
           </property>
           <property name="text">
            <string>Dog</string>
           </property>
          </widget>
         </item>
        </layout>
       </item>
      </layout>
     </item>
    </layout>
   </widget>
  </widget>
 </widget>
 <resources/>
 <connections/>
</ui>