ABL mesh fails half way through G29

[xxKeoxx]

I’m having this issue which I can’t resolve. Probing begins with G29 and seems to be going fine. Then suddenly around halfway through probing the bed, the bed drops down like it should, the probe moves over and deploys, and then the probe retracts and deploys. This throws the M999 error.

I’ve checked connections on everything so I’m struggling to understand what’s going on here. Can you help?