LAN Controller version 1.2 SW:2.43

[FaneBranesti]

version 3.xx don't have watchdoog
version 2.xx have watchdog
you may use 3.xx or 2.xx on this HW.

OK. Thanks!
I will firstly try 'V2.59 (Filename: lc10_v2_59_HW1_2.bin (322.4 KB))

I updated to V2.59 but it behaves in the same way...
Do you think that  a problematic UTP cable may produce such a behavior? The controller is connected to the router with a cable of about 30 m. 
Does the browser interface need a better connection quality than the mail client?

Browser interface don't need high speed, it is about 80kB/s.
It is hard to say what could be the cause.
Maybe you will try a new version with more possibilities?  https://tinycontrol.pl/en/lan-controller-35/

I had in mind such a possibility, but I am afraid that it may behave in the same way. I have two such controllers and after they work perfectly for more than six years, suddenly both of them started to behave in the same way, even I updated them at all available firmware (the version without watchdog included). I started to think that it cam be something not related to the controller itself, but I cannot understand what. Since it can be supplied with a big range of voltage I tried increasing from 12V to 24 but no change in behavior.

Anyhow, thanks for your intention to help!
If any idea, even looking strange, please do not hesitate to make a suggestion.

P.S. When I am at home (connected on LAN) and it does not work, I can use your specific application able to find it and reboot. Apropos, is there a way do do that from external IP?