Prusa Mini - Under and Over Extruding - Now no longer extruding at all. Please help

Hello, I really hope you can help me!
I have x3 Prusa Mini's which I received in Sep 20. I have been using Yoyi Silk Green PLA 1.75mm filament since I got them as this is the colour of my company's brand. I bought the Prusa Mini's after running x5 Ender 3 Pro's for several months but I've had massive issues with warping so I decided to buy the Prusa Mini's instead and have never looked back! However, about 10 days ago, one of the Mini's stopped extruding halfway through a 2hr print (and halfway through a reel). I couldn't figure out what was wrong and no matter what I tried, it just wouldn't print. Then about 5 days ago another Mini started with the same issue. It either under/over extrudes like in the photo in a stripy pattern, or it just doesn't extrude at all. The gears are turning in the extruder but the filament isn't moving at all (the printer carries on as though it is printing). I have cleaned out the nozzle, done a cold pull through the hot bed and I've cleaned out the extruder/gears (multiple times) but nothing seems to fix the issue. As a way of eliminating all possibilities, I tried a different filament (the free Prusament sample that came with the Mini's) and the problem goes away. ???? I have contacted a local UK based filament manufacturing company to have the colour I use colour matched (as Prusa don't do anything similar) and I tried their sample and.... you guessed it...! It sometimes extrudes, it sometimes doesn't. I honestly don't know what to do. They have Prusa's and Ender's etc that they test their filament on and they even track the +- deviation of the filament per spool which you can track like you can do with the Prusament. Is my machine now too sensitive for some reason?
Has anyone ever seen anything like this before? Do you think it would help if I somehow managed to change the gears in the extruder? Why would this start happening after months of absolutely no issues whatsoever? Could there be something else that's causing this that I've not thought of?
I now have only 1 working Prusa Mini and I'm dreading having to change the reel. If I knew of somewhere local that I could take it to (covid permitting) or something such as a service centre in the UK that I could send them to then I would, as production of my products has almost ground to a halt.
If you have any thoughts, advice or if you have seen this before then I would really appreciate your help.
Thanks
Jemma x

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sounds like a possible covid issue.

Ie: whatever pigment was being used has now been changed to a different chemical or additive.
The original either getting too expensive or just becoming hard to get.

Particularly if a different filament works fine in the same machine.

As was mentioned try different temperatures and different print speed.

having had several long chats with filament manufacturers - different colourants do effect filament properties.

You might also try the same colour in pet-g or pet.

Or - god forbid - even abs.

In the short term the answer is obvious.
Use a different colour :-)
And blame covid - that way you also get a sympathy vote.

You know I must have well over 100 spools of one type of filament or another in here - and not a single one of them is green.

So green is probably not a massive seller and it would make sense for there to be supply issues at the moment.

Just be grateful you're not in the computer industry. I wish I could just change colours to get supplies back !