flash player working for 30 secs in evenings???

Actually, I just re-read your original post and didn't catch the bit about it crashing, which is bizarre.

A couple things come to mind.

There's this classic story about a company where their computer crashed every morning at 9:15.  Turns out that it shared the same circuit with mechanical equipment that was on a timer, and the electrical noise on the circuit caused the computer to behave erratically, in a super consistent way.  Putting the computer on a UPS or moving it to a different circuit might isolate it from electrical noise.  If you move it to a circuit where other computers are behaving normally and the problem goes away, then a UPS (Uninterruptable Power Supply) is a pretty cheap and effective way to clean up power going to that computer.

Microwave Ovens interfere with other microwave signals, like WiFi networks.  If your problem computer is closer to your neighbor's house/apartment than the others and they consistently microwave dinner in the evening, that might create adverse network conditions for one of your computers.  Similarly, if they're close to you and using up lots of wireless bandwidth, that may impact your connectivity.  If the other computers are wired and this one isn't, or they're all wireless but have better reception with the router, that might explain the issue.  You can try using a wired ethernet cable or moving the computer around to experiment.

You might also just have a bad piece of hardware or driver, or you're running something on that computer that leaks memory such that Flash is crashing because it can't allocate memory.  What happens when you reboot the computer?  Does the crashing persist, or is it good for a number of hours after?

Since it's actually crashing, a crash dump would give us some super useful information.

https://helpx.adobe.com/flash-player/kb/report-flash-player-crash.html​

My guess is that external network pressure (congestion/interference) precipitates a sub-optimal network condition (high latency, high packet loss), which probably tickles some kind of edge-case in the video code (e.g. error recovery code) that leads to a crash.  That code isn't hit under normal network conditions, but you're seeing it consistently when network conditions degrade during peak viewing times.   A crash dump would give us a definitive answer.

xtra info:
It is only when viewing HBO Nordic movies/series and nothing else at all... everything else that uses flash works even simultaniusly...
its only in the evening(after 20:00H) and only that one particular computer... it dosnt compute what so ever.