How to interpret Hardware watchdog exceptions on a ESP chip?

For one of our Projects we have a Hardware Watchdog reset which happens on roughly 0.1% of our devices each day, resulting in many unwanted hardware resets.

We are trying to figure out what causes this Hardware Watchdog reset, but have failed to find anything relevant in our code which would result in this behavior.

We are using the Arduino 2.4.2 Version, we are not sure since when the Problem has bugged our solution since we had other issues which have now mainly been resolved.

Luckily our devices send us their reboot reasons when they reconnect, there we are receiving the following:

ResetReason=Hardware Watchdog;ResetInfo=Fatal exception:4 flag:1 (WDT) epc1:0x40102329 epc2:0x00000000 epc3:0x00000000 excvaddr:0x00000000 depc:0x00000000;

We have looked for any thing, when this through the EspStackTraceDecoder we ended up with:

0x40102329: wDev_ProcessFiq at ??:?

A search looking at varies project which have asked similar questions mostly seemed to include a dns query. But not all, so it seems to be a general issue?

What additional information could we extract that might help us identity the issue?

Some Additional Information

• Memory is stable and we have ~15-17Kb of free Heap, depending on the mode and the amount of data queued to send / receive queue.
• Our side of the code uses yield, delay etc. so the S/W watchdog should always be fed. This also applies to the Async callback code.