Well if you have been using this for 2 years then it would be time to replace the hotend and peek tubing if it is not an all metal hot end I can generally get about 4 months from a tip without quality issues the peek tubing tends to get worn over time and also when you replace them you must tighten the new tip heat the hot end then tighten again or else it would just clog . all metal hot ends are a great upgrade they last much longer but tightening them correctly is very important . if there is any place for the filament to seep into the threads it will clog almost instantly
I run a Rep1 Dual and I would agree with funkshin. My prints that lost material part way through were all due to the filament getting snagged or too much friction in the feed line. A little oil helps - also make sure your spindles can turn freely.
Could you check the filament is still correct size? I have had filament printing fine, and then dia is slightly larger as i used the reel. If you just extrude well above build platform does it extrude perfectly? Straight out, not to one side? Finally, have you recently cleaned the drive gear the pushes filament out?
I had a similar problem with a rep2 and finally it was the extruded fan not working at full speed, try replacing the fan, they are cheap and you don’t have anything to loose.
Try a different (newer ) spool of filament. It may have absorbed water. Is it only with one extruder or both? I have had this issue before on one extruder. The temp readouts looked okay but I decided to swap left and right heaters anyway. The problem followed the heater. Bought a new heater and the problem hasn’t returned.
Just an update, I changed the fan and it didn’t solve it.
I was finally able to fix the printer by changing the spring on the plunger, I believe the tension wasn’t enough to drive the filament. so changing it did the trick.