Did you ask them for a specific timestamp or log of the system error? I mean, it sounds sketchy that they'd just cancel an order during a Friday selloff like that, especially with no heads up. Idk maybe it's just me but I'd be pushing them hard for a written explanation or some proof that it wasn't just them covering their own positions. Did you try asking if they have any records of the order getting queued or processed before the cancel? Feels like they're hoping you'll just drop it and move on, but if this was a solid trade, I'd want to see the actual error message or system log they're claiming.

What pump size you running with that 12-inch cutter? I'm wondering if a bigger pump would help even with slow swing speed.

Yeah, did you try giving them a tiny bit of slack? I did that on my stock wheels and it actually helped. Snapped one myself a few months back and since then I just back the tension off a tiny turn on each spoke.