Hello, so I have an early model Anycubic i3 Mega (with the 8-bit board), upgraded with silent stepper drivers and the official i3 Mega S extruder upgrade kit. It's been having trouble printing for a little while (mostly not pushing enough filament, even during filament changes) and for a variety of reasons that we've always managed to fix, but this time I'm at my wit's end. Here's a rundown of everything :

• Shortly after upgrading the stepper drivers, it wouldn't push enough plastic; upping the voltage to 1.2 and calibrating e-steps fixed it and it worked like a charm for a while.
• It then slowly started to get underextrusion issues, but it seemed like the cause was the filament getting stuck in the PTFE tube, like there was too much friction somehow? Oiling the filament fixed it, it was meant as a temporary fix and it slowly started not being enough, leading to the next point;
• I tried changing the Bowden tube for a Capricorn one - I'd heard good things about it. It didn't fix anything, so I thought the problem might lie in the hotend. After cleaning the nozzle didn't help, I changed the whole hotend for a spare, no dice. I changed out the Capricorn tube for a regular, new, PTFE tube, and still no dice. We increased to voltage to 1.3 and it still doesn't push enough plastic.

And this is where I am. I probably skipped over a couple troubleshooting steps along the way but the major changes should be there. I'm just not able to print at all, the filament comes out wispy thin, and even cranking the extruder tension all the way isn't enough.

Thanks in advance for your help. I am open to any suggestion.