did you ever consider their code was good and it's you that is the problem?

I did, and that is very much not the case here.

I don't know how a "good" programmer opens the same gig+ file for writing in multiple threads (dozens sometimes) without any kind of concurrency management.

A "good" programmer doesn't give you a 2000+-line python script where every variable has no more than two characters in its name, with 0 comments or explanatory info.

A "good" programmer doesn't write a cluster that checks an "OK" REST endpoint on a regular interval, and then have that same cluster freak the fuck out and check 10-100x as often if that "OK" does not arrive exactly as it should.