I have always just turned on the floating button, so no matter what I was doing on the phone, I could press the semi-transparent OCR button, I really didn't use it any other way. My phone usage habits never really changed either, played with with Pleco settings, been doing the same thing for years. My only guess is maybe when I let android update to whatever is the latest, something clashed with Pleco? As of now its on One UI 6.1, Android version 14.
--(just realized you could have meant it this way) if you meant activating the screen reader, I would long-press the floating button and choose "show reader icon"
I just tried rebooting the phone to see if it would reproduce the bug. It does reproduce the bug, after reset I am back where I started with the floating button vanishing after pressing it (currently just have the OCR button visible). Now I can check your other questions, and finally I'll try the same thing to "fix" the bug after.
If you go back (button or gesture depending on your phone configuration) after the button disappears, does it reappear?
Pushing the back button does not make the floating button reappear, I see why you want to check this, its usually how I would exit the "OCR" mode and remove the green border of OCR.
Also, if you tap on the Screen Reader sidebar menu item again after the button has disappeared, does it reappear? If so, when you then tap on one of the buttons in it, does it disappear immediately or does it prompt you to turn on the accessibility service?
After the floating button disappears, if I click the sidebar menu to turn on screen reader/ocr, first press does nothing, second press does make it reappear (assuming that means its still "open" and i'm closing then reactivating the button), and there is no prompts for accessibility services (under normal circumstances I do get that prompt the first time turning it on after phone reboot -- also note this time after reboot first time activating the floating button from sidemenu also did not request any accessibility features). Same behaviour, just click button, button disappears.
Oh and one more notable thing, after the button disappears, if I turn the phone screen off and turn it back on, the button returns. Not sure if there is any other circumstance it returns, but have noticed the button will return after some time.
Hope this helps, let me know if I check anything else. Really appreciate the app, it is fantastic.
EDIT: Oh forgot the mention, if I do what I did the first time to "fix" the problem, it fixes it still, as soon as I did what I did mentioned before, everything works as expected and I assume it probably will until I reboot the phone again.