This sounds exactly like what I had with my TronXY X5 a while ago and with PLA. I got under extrusion and a lot of clicking from the extruder. I ignored it and just increased the temperature. The clicking was gone for a while and then it worked for a while before it got worst. I knew what was wrong, but I was just to lazy to fix the issue. I knew I caused it when swapping between ABS and PLA a alot.
I think I told this here before: Your heatpipe/heat break is full with gunk, which is reducing the diameter where the filament needs to go through. You probably printed PLA before and swapped the filament, but not all PLA got out. It burned on the inside and is sitting there. The reason that higher temperatures work is that the closer the filament gets to the heater, the softer it becomes and you are pressing it through the trouble zone. Thats where the extruder works hard and looses steps you hear clicking. The gunk itself is no longer melting. It is just growing slowly in your filament path like a tumour.
When swapping filament from a low temp to a high temp version you should take caution. Best scenario is to heat the block up to a temperature both filaments can be printed with. It does not matter of the print would look good, just what is mentioned on the package. An overlapping temperature range.
Now push the old filament by hand into the hotend and rip it out fast again. This will ensure you got most of the stuff out. Now insert the new filament and push it in. When you feel it is melting, pull it hard. You will see there is still old filament on the tip of the new filament.
Cut the blobby end and repeat the process a couple of times. It is a good idea to pause a few minutes and repeat the process. This gives the filament inside the hotend time to sink down into the melding path, where you can catch it on the next attempt.
Some resellers are selling expensive “filament to clean and prime your printer” before the next print. That is just bullshit. They just sell you 20g of transparent filament for 12$. I even saw some youtuber praising the stuff, because they got sponsored hard. Do not fall for that.
If you have transparent filament or a rest of it, then you can use it the way described above. The advantage is you can see the pulled out grunk better and leftover transparent filament blobs will not be visible in your print. But remember the transparent filament needs to be in the same temperature range as the filament you want to print, or you just create gunk from transparent filament.
The important thing is to not cook the low temp filament when swapping filament types. The ash will get caught, form a solid blob and may even burn into the bowden tubing with its sharp edges. Creating dips and dimples on the way out, if it comes out at all.
You may get away with a simple filament swap, but over time you create a clogged hotend.
