[Mark McLeod]

That is odd behavior, since only your first and last drive commands actually do anything. All the intermediate drive commands just repeat what the first one ordered, so there should be no change in what the motors are doing.
There are no drive stops programmed in.

I can't see the time delays you have in each drive frame, but I suspect they are longer than the Watchdog is willing to wait before disabling your code. You need to be using Watchdog Delay & Feed during long periods of delay.

P.S.
In future postings just attach the vi itself. We can open and read that.