There have been lots of comments on FaceBook about the azimuth drive disengaging from the drive belt because the base and dome are not perfectly round and concentric. There are two issues here. First it's very hard to get pieces of ABS plastic 8 ft. in diameter to stay truly circular within less than 1/4" given changes in temperature, etc. Second, the track that the dome wheels run in is wide enough to cause some shifting. First, try to get things as round as possible, but this is my ultimate solution to the drive cog coming off the dome's cogged drive. The white steel bracket used to be one piece. I sawed it in half and added the hinge. The unit slides on the bolt that goes into the wheel and is held against the dome cog by the spring. This solves the problem of the cog slipping when the dome moves away from the drive cog by allowing the drive cog to also move a bit.
@Jason Newton looking good with your mod of this! I think for me the hardest part was finding the right spring. Fortunately one of the local hardware stores has a wall of springs of different lengths and gauges. So far the one I am using is working out well.