Robduarte I experience this in some apps, not all. Some websites, not all. Some PDFs, not all. It seems dependant on how text is presented on the app/site/file. Idk if there's a workaroaubd for this; I just accept it. The "Read text on images (beta)" feature doesn't seem to work in any scenario but I would think something like that would solve it.
It's likely that the app you're using displays text in a way that Select to Speak can't detect.
Edit: I see you said "any" app you try this in has problems and that I have not experienced. I'd try reinstalling the accessibility suite and if that doesn't work I'd feel very sad because I don't have teck skills to troubleshoot further.