Reinstalled extruder, but now getting under-extrusion: causes?  

Reinstalled extruder, but now getting under-extrusion: causes?

Hello!

About 2 hours into a print, filament stopped coming out. Sounds like a block, right?

After cancelling the print, I heated up the extruder to PLA temp, and went into settings > move axis > extruder. The filament reversed back out okay, but when I increased the value it seemed to stop up against something.

Clogged hotend?

I gently pushed the filament whilst increasing the value, and then filament started to extrude again.

Does that mean it's unclogged now, and I can carry on? Or should I address the initial cause?

Also I noticed that the layers were not very well stuck together. I was printing a project box, and the sides had started printing but they just lifted off the base.

Sounds like classic under-extrusion right?

What is the cause of these two things?

Here's the background:

This was my first print after reinstalling my hotend to the extruder, after replacing the heater and thermistor blocks.

I also took the opportunity to replace the PTFE tube with a new one (sourced from Prusa shop so it should have the correct angles and cuts etc)

Calibrated ok and things seemed fine. I ran a long print and set up an electric heater nearby my enclosure as the enclosure is near a window and it can get drafty (temps of around 2 degrees in the nighttime here).

There seem to be quite a few variables so I'm not sure where to focus to prevent these two problems happening again?