iPhone 5s display behaves strangly on swipe/click For 3 days now, my iPhone 5s has some strange symptoms. 

When I click or swipe on my phone, sometimes it's not doing what I expect. I can click and swipe, but my request either gets ignored or something completely strange happens (like opening a random app or options etc).

Here are some symptoms that I can reproduce whenever my phone is not working:


I can always press Home and see all apps, but I can't close when I swipe from the top; it's just ignored.
I can't turn my mobile phone off. The swipe from left to right that is needed to shut it down is ignored.


Sometimes my phone is working, and sometimes it acts as described above.

I tried the following to fix it:


Shut phone off and start again.
Restart phone with holding Home + Power for 8 sec. This is the only option that I have when phone is buggy. After restart the phone always works, but after a while it shows the symptoms again.
Reset phone to factory reset. After restart the phone always works, but after a while it shows the symptoms again.


I have also upgraded to Version 12.1.2(16C104) (was before on 12.?). 

I don't really know why its not working. My last hope is to downgrade it back to 11.*, but the bug has only appeared in the last 3 days and I have had version 12.? for quite some time now. Also downgrading the phone is no long-time solution. 

Are there any suggestions what I could do to fix this problem?

Also, in order to download version 11.* I need to know if I have a Global or GSM model. At the bottom of my back of the phone is nothing as suggested here: https://apple.stackexchange.com/a/85943/318324 in my settings I found that I have the model: ME341LL/A
This sounds like the digitizer is failing.

The digitizer is a "glass layer" that sits on top of your LCD display to accept input (taps, swipes, etc.).  This can begin to fail for any number of reasons from physical damage, to water damage or even aging.

The iPhone 5S has the digitizer and LCD as a single assembly, so to replace one, you'll have to replace both.  iFixit has an excellent guide on how to do this.  However, if doing this type of procedure is not your cup of tea, you should take it in.

(Though the 5S is 6 years old now; it's probably time for a new phone).