Align printhead done, but still prints misaligned. (Epson T50)

My printer is actually an Epson T50, but I couldn’t find the correct one in the list.

My problem is when printing text, I get a double print (vertical alignment) in particular at the top 30mm of the sheet. Probably about1mm out of alignment. Also minor double images towards the middle and bottom of sheet. I’ve done the Epson alignment procedure numerous times, modifying the numbers to get it slightly better each time. Then I can usually get it pretty close. If i print a page of text after that, it’s still ok. Bu the next time I come back to print (a day or so later) it’s back to being misaligned again. Is this a printhead issue that can possibly be fixed? I’ve never removed it and cleaned it, only done the printer cleans. Would the maintenance tank have something to do with the issue? I run a CISS ink system which I don’t think has anything to do with it, as the printhead runs smoothly when connected to it. Any help would be greatly appreciated.

Thanks in advance.