With these various (partial) failure modes, anomolously hot modules, etc I would always try a quick check of the current, the voltage at the head of the string, and the voltage at the tail of the string (with white and with all off), before cutting any modules, and report those results too.
Then you know whether to focus first on power or on data. Not that there can't be strange cases which are harder to troubleshoot, but it's good to zoom in first on the most likely things.
And of course you have a major advantage with 5 strings of 20 - you can plug and play.