Screen flckering after inactivity (energy save mode)

Hello all, new member from Germany here :raising_hand_man: ,

I'm running Ubuntu Mate on a Raspberry Pi4. The Pi is connected to my LG 42LN5758 42''TV.
The Pi runs 24/7 and sometimes I use the Pi as a desktop station with the TV.

I have some issue with screen flickering after the energy save mode on the Pi:

After some inactivity the video output of the Pi fell into energy save mode. The TV turns off. After that I start my TV and I press some key to awake the Pi. The Pi awakens and on the TV is screen flickering.

I figured out the TV screen is not properly detected. The screen settings tool says I have an 72'' Goldstar TV, but I have an 42'' LG.

I connected my Pi with my Benq computer monitor and this screen setting tool detects this monitor perfectly. After the energy save mode I don't get any screen flickering.

I tried to adjust the screen settings with arandr: During the screen flickering on my LG I singed in and I started arandr and the screen flickering disappears without any adjustment on arandr. Then later after a new energy save mode the screen flickers again.

So I have to start arandr after every energy save mode. It works, but I want to solve the problem perfectly.

On startup the Pi don't have the screen flickering. Only after the energy save mode I have this prob.

Do you have any suggestions for me? Thanks in advance

I found a solution. Its not a perfect solution, but it works:

I have to lock the screen with Super(Win) + l before I leave the Raspberry.