Geeetech

Every now and then some dirt drips from the nozzle (see attached pictures)

I'm not the first one reporting this.

Is there any fix for this?

I think you should check the wiring of the cooling fan and see if it work or not
Then you can check replace it with another nozzle for a test

I got dirt from the nozzle quite a few times - I believe its because of erratic temperature monitoring where the head gets so hot it burns the PLA or the head starts leaking :(

I changed the head and this worked for a while; now the new head is starting to do the same. In my opinion I don't think these replaceable heads work very well - check your temperature as the job prints and see if it jumps up and down (mine jumps from -1 to 220 every few seconds and then pauses the job several times to report there's a nozzle error!)

I've re-seated the head many times but still have the same problems. I hope there's a fix for this too!

I think you need to clean it before it starts to print