'Thick line' issue with Anycubic Mega 2.0

[swam]

Hi,

I've now had three Mega 2.0 machines, and they each have an issue with printing. Around 8-10mm into a print, they produce a thicker wide band of material, no matter what file I print. The machines have been setup to the instructions, I've made no changes in Cura etc, and I am using the profile provided by Anycubic themselves. I've even tried other settings in CURA and every time I get the issue.

I contacted Anycubic support when I had the issue with the first machine, and they said it had to be an issue with the Z-Axis thread, so I returned the machine but have now had the same issue with TWO other machines.


I purchased these machines from Amazon. Do they have a dodgy batch in at the moment, as it's the only reason I can come up with as even the tech support person at Anycubic said getting three machines in a row with the issue is like "winning the lottery".

I've attached a couple of pics so you can see what I mean.


Any ideas or possible reasons/fixes would be much appreciated.


cheers

Sam