As a real-time embedded systems engineer, I can tell you that coordinating tasks and timing can be a challenge for a small system, let alone a complex system like RotR, even for the best of the best engineers. You can only test your code to a certain degree until you get the full system up and running, and even then there are just too many circumstances to foresee until the rubber meets the road in full testing.
While Disney has done plenty of timing scenarios on attractions and has a few trackless systems under their belt, it seems like this is the most intricate trackless timing system they've attempted to date. Even IJA after 24 years still goes down a lot because of timing issues. I've had to create from scratch the design for a reduced instruction set processor in school and it took me hours to track down an issue in the Verilog code because I misspelled something wrong. Look up priority inversion and the Mars Pathfinder project and how it completely died while on Mars because of one single line of wrong code.
They'll get it working and it will be great. I just get frustrated when non-technical people say negative things and think that Disney engineers should be perfect and that problems can't arise.
P.S. while I replied to you
@britain none of this was directed toward you, but to the public in general.