Hi, we welcome you to our Community!
I'm sorry for what you are experiencing using your device.
By carrying out tests with our laboratory devices I did not encounter the anomalies reported when saving screenshot in PNG format.
In order to be able to exclude any conflicts arising from the presence of third-party apps installed on the device, I suggest you check if you encounter the same situation by booting the device in safe mode.
In this mode, most third-party apps will be blocked, so you can check, using the main functions of the device, whether the anomaly found is due to a conflict created by an external app.
If what you find does not persist in this mode, there is at least one app on your device that interferes with correct functioning. You will therefore have to gradually eliminate the installed apps and, at the same time, check the behavior of the device.
To access safe mode, simply follow the procedure indicated on this link:
Keep us updated on the outcome of the test. 
Hello!
Hello @xzkl,
thank you for your answer.
If you didn't have any issue when you tried to use your phone in safe mode, than this could be a signal that the interferences come from a third party app (and by that I mean also apps like Instagram or Whatsapp, which you mentioned). First of all, you should check if any of these apps needs an update (if it is so, that could be the source of the problem).
Otherwise, if the third party apps have been already updated and also by taking into account that the issue came up after the update of your device, you should consider doing a factory reset. Remember to do a general backup of all your files, pictures and notes (etc.) before the factory reset, in order not to lose any of your data.
Let me know if it works this time! 😄
Have a nice day 🍀
Ciao @xzkl,
if you decide to proceed with the steps recommended by our colleague Andrea above, please keep us updated on the outcome.
We remain at your disposal.
Have a nice day! 😊
