Filament jamming - Anycubic I3 Mega

So I've been pulling my hair out over this as I can't seem to figure out what the actual problem is here.
I own an Anycubic I3 mega (had it for almost 1 year), and my fillament recently has been getting stuck in the teflon tube. It's not a nozzle clog as the fillament actually stops about 7/8 of the way to the actual print head. If I pull everything apart and replace the tube it's fine for a print or 2 then it just gets stuck again about halfway through a print. Has anyone else had this problem beforehand?

We have recently brought different filament (cheaper) and it has played up so not sure if that could be an issue either