We’ve had similar problems sometimes with the Tough 2000. Some cartridges have resin that’s fairly thin and has no issues with the mixer. Others are fairly thick and decouple the mixer every other sweep. We even had one incident where it decoupled early in a job and the platform came down and impacted the decoupled mixer. We were confused why the printer didn’t auto stop because if I recall, if the mixer decouples during a sweep, it detects it. So we’re guessing this happened because during the left sweep to nest, there was a lot of thick resin that built up on the left side of the mixer on the final sweep, so when the LPU released the magnets, the weight/pressure from the resin build-up on the left side of the mixer shoved the mixer out of nest towards the right and under the build plate.
One thing I also find with Tough 2000 is it seems to produce details a bit oversized. That is, if you have mating parts, you might need to sand or trim down your parts to get them to fit together because the fit is too tight. You could try Tough 1500. I’ve found this resin to produce parts closer to intended nominal (I’ve mostly only done fairly small and thin walled parts). Keep in mind, the tough resins apparently eat/damage the tank bottom layer over time, so the tank lifespan is shorter than if you were using standard resins.
Most importantly, you should print knowing what your parts will be used for. Does it have to be a tough resin? Or can you get away with using white/black/clear/grey? Tough is good for really thin wall sections and parts you need to not crack/shatter as easily. Otherwise, you’d probably want to use one of the standard resins.