I have this issue on my Galaxy S9+ since the last update. Same thing green screen, back screen or flickering between the two.
I think I have the trick to unlock the phone in "normal mode" (no more flickering, no more green) for me it worked and didn't have any issue since.
First use the other methods found on the internet (max brightness or lowest brightness) to at least have the possibility to see what are you doing on step 1.
Step 1. Make sure "Always On" display is turned on, and "Tap to Show" option active (Other options made it impossible for me to use my phone - entire display was green) - Can be activated from Quick panel
Step 2. Lock the phone (right button)
Step 3. Double tap to wake up screen, then double tap on the bottom square to unlock with pattern/ fingerprint/ face recognition/pin whatever you have set up (DO NOT USE Button to wake up screen or fingerprint to unlock directly).
This worked for me and all I have to do now is unlock the screen only by double tapping.
Now in my opinion this is a software issue and if someone from Samsung is actually reading this maybe can have a look at past updates.
Why software/ firmware ?
1. First of all It happened right after last month's update when the phone restarted to update all went green
2. Never dropped my phone + I have a clear view book case for protection
3. If it would have been permanent I would have blame it on the display, but the above fix works every time for me
4. At first I thought that there is something wrong with the unlock button, but it also happens if I directly unlock it with fingerprint sensor... (if I double tap then use the fingerprint everything is ok).
Hope the above is a temp fix for everyone until Samsung figures this out..
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