Ty is probably right about 1 of the MOSFET level shifters being bad. If that's the case, simply swapping in another WiFi module will do no good because the level shifters are on the main board. Luckily, those parts are small and inexpensive. Removing a surface mount part is not too difficult. When replacing it, be mindful of static and how much heat you apply.
I would get both the WiFi module and the level shifting MOSFETs from Ian and start with the simple swapping of the module just to see.
After leaving the clock powered down for a couple of days i decided to try and set it up manually, without using wifi.
When i powered it up, it just took some seconds and it went to the correct time, but all the other settings was obviously back to factory, so i tried to connect, but i am not able to connect via the IP even though it shows in my router as a device, just get a adress not found error.
Anyway i set up everything except the time manually and everything was golden for a couple of weeks.
One night it went black, so i tried some movement in front of it without success, rebooted it, an discovered that it will not see any movement from the PIR. So i set it to no blanking and blank LED only to keep it on.
I have then discovered that the PIR register movement during daytime (the dot on the seconds tube lights up) but sometime after 1900 it stops detecting movement.
And today, another couple of weeks later it first started to flash sometimes one LED, sometimes all LEDs and sometimes show the software version. After doing this for a while some of the tubes started flickering, and one tube (minutes) went almost completely dark.
So now i powered down again and dont know what to do.
I tried a different psu (12V, normally been powered by a 9V). It just flickered a couple og times and then went all black on tubes and LEDs. At this point i did not have the case open, so i dont know if the internal LEDs where on or off.
I opened it to check for anything obvious, i can not find anything, but the inductor(?) in L2 might have some small burnmarks at top:
I also measured the voltage of the psu, when unconnected it measures 9V flat, connected to the clock 8.94V, the LEDs on the wifimodule lights as normal, also the mainboard LED lights normal, but all tubes, tube LEDs and neons are flickering like crazy, but for the most they are black.
I made a video, but it seems it can not be uploaded here?
For video you need to upload it to YouTube or similar video sharing site (I suppose FaceBook or Insta would do) and then post a link to it here.
That inductor in the photo is probably okay. That's L2, it's part of the 5V regulator circuit, not the HV circuit. See schematic. It would be useful to measure the +5 volt rail at the VCC and GND test points, at the far left end of the board, while the problem is occurring. If the 5V rail is unstable I'll change my opinion about the inductor L2.
BTW - I looked at L2 on my two modular clocks, Both have the "notch" on top (at 7 o'clock position in your last picture) but not the other crusty skidmark features. Not 100% sure what to think of those. It almost looks like it got wet or maybe spattered with solder or flux ??? Or maybe it fried, hard to say.
Look into it later when the dust is clearing off the crater.