Who gets a flickering

[zimma71]

Screen flickers when phone is doing background work.  

This can't be good for the screen .

This phone is terrible on reliability 

The screen has gone from being over sensitive to under sensitive

I often have to click on things twice now or the text comes out on the line of previously on it's become very annoying who's used to be the best phones on the market TN

[BandOfBrothers]

Which model of the a series are you using @zimma71 

Have you tried any troubleshooting advice such as Safe Mode which disables downloaded apps , themes and 3rdcparty launchers  https://www.samsung.com/uk/support/mobile-devices/how-to-start-my-galaxy-device-in-safe-mode/ or clearing your phones system cache files.

Clear your System File Cache via the instructions in the Samsung Link. You may need to hook upto a computer or insert your headphones to get to the recovery menu. https://www.samsung.com/uk/support/mobile-devices/how-do-i-clear-the-cache-on-my-device/ 

Check everything is updated in regards to your software and apps and if absolutely necessary back up and factory reset.

Finally a Samsung Experience Store  / Samsung Service Centre can take a look at the phone.