My apologies. I frankly know less about sublimation ink printers than about laser printers.
So some of the advice I have offered so far is completely inapplicable! and I apologize.
But, in a way, that should make the task much simpler. In a non-laser-type printer (whether heat-transfer, inkjet, or sublimation-ink) you need to be careful mostly of one thing: touching, breaking or contaminating the printhead. The 'drum', is of course, nonexistent in such printers.
Re-reading your question's original posting with care for all details... it sounds actually rather like a laser printer problem: parts have become out of alignment with each other, probably owing to rather less than gentle or otherwise improper paper removal after a jam. And you mentioned a 'belt', which also suggests a laser printer.
I honestly do not know how to re-align this sort of printer, if the parts need re-aligning or the like. Usually the printer should re-align itself - which it has failed to do.
If there is a belt, there is a way for the printer to 'read' the belt's position.
If so, then it may not be the 'sensor' that 'reads' the belt's position (possibly by a tin-foil-like silver reflective patch or square on one edge of it) that needs cleaning, so much as that path that the sensor 'reads'.
But again - I am not sure I know my way around your sort of printer. I am advising you on general principles. Would you like to continue with me, or should I Opt Out of this case?