LG refrigerator LFXS28968S won't drop ice into bucket

I have an LG refrigerator model LFXS28968S/11 (ASTCNA1 variant) that won't drop ice into bucket. If I remove the ice bucket and press the test button on the ice maker, the ice tray rotates completely and drops ice. It then returns to home position and fills with water. The water then freezes, the tray turns a tiny bit like 10-15 degrees - then stops.

Its under warranty still. They've sent someone out twice and it still doesn't work. They replaced the ice maker (just the ice maker - not the entire assembly that includes the interior door panel and bucket auger motor) and the new ice maker behaves exactly as the original one did.

Second visit they replaced the main logic board on the back of the fridge, I also got a new ice bucket, and they came with a new ice maker assembly kit - this part includes the interior door panel and the auger motor, but it was the wrong part. Looked identical, but the connector on the harness was different, so it wasn't installed. But same thing after logic board replacement - tray fills with ice, it starts to rotate ice tray when it's frozen, but it stops rotating and doesn't get anywhere near far enough along in the rotation process to drop ice.

Any ideas what could be the problem? I do wish they had been able to replace the whole ice maker assembly kit, since the more complete kit with the door panel includes the optical sensors that tell if the ice bucket is full. I was wondering if those were bad and they are why the ice tray stops part way. I posed this hypothesis to the repair technician , but he believed if the bucket full sensor was tripped that the tray shouldn't attempt dropping ice at all, which seems reasonable to me.

This 2.5 year old LG fridge replaced a Samsung RF263BEAESR/AA fridge that Samsung bought back 100% due to five service visits over ice buildup on the fan and evaporator coils. Because of that experience I got an extended warranty on the LG.