Consistency issues with the A10T

[RitchievanDaal]

Dear Forum,

I purchased the A10T a while back to do multi-material prints.
The printer works pretty well, when running at all.

However I do have a few problems with it that I cannot solve;
I've had a massive nozzle clog in the past, this printer is mostly used for single nozzle prints and I use Cura's Ender 3 profile to program it.
I've found that the A10 profile is absolute trash.
This nozzle clogg keeps occuring because all 3 bowden tube ends are heated simultaeniously, so I replaced the clogged up bowden tubes and now use a purge cycle for all three extruders.

This seems to work okay, or at least seemed to work okay. Now I'm stuck with massive underextrusion again...
I have no explanation for this.
I both reduced and increased the extruder pressure.
I checked for obvious cloggs, nothing can be detected.
I checked the bowden tubes, these were still okay.
I swapped out the nozzle for a new one.
I used different temperatures ranging from 195C (which normally is fine) up until 240C, with PLA.
I used varrying speeds ranging from 40mm/s up to 100mm/s. An increase in speed does exgaggerate the problem, but lowering it doesn't solve it.

But I just feel excessive backpressure when manually feeding the filament... As if there is a clogg somewhere.
And this leads to a lot of failed prints...
I however have no idea what could be wrong as I have already excluded the obvious issues which I have had before.

Then there's another problem,
Whenever I'm printing at speeds higher than 60mm/s I get Y-step skipping.
Again, this is an issue I not have had before. Even when printing at 120mm/s with this machine.
I've already altered obvious settings as printing temperature to avoid blobs and even the speed and tightening the belts, but this doesn;t solve the issue.
I checked if there are no physical obstructions, but the axis runs smoothely.

I haven't changed any firmware, the only change is that I had a custom profile set-up in Cura,
But then obviously Cura crashed all my profiles which it does every week or so and now I use the standard Ender 3 profile.
This has worked perfect for 2-3 weeks now, until last week.

I really do not know what this is. And how to solve these problems, as they just occured after the machine
I hoped to be able to use it as a production machine, as a back up to my Ender's. Not only as a dedicated multi extrusion machine.
But the printer is printing really really inconsistent, up to the point that I almost chucked it through the workshop.
I get a successrate of maybe 50% at this point. Where it had been closer to 95% when everything is running properly...
Kinda feel's like Schrödingers 3D printer, the moment I walk away from the print has just so failed as it has succeeded...

Any help would be appreciated, or is this just something that is a 'A10T' thing?