Blue Iris

Oh guys we've got a big problem

First, the "source file corrupt" dialog indicates that he is not using Direct-to-Disc recording format, and does not have the codec installed to export to mp4. Best practices are to use D2D unless you have a reason not to. No offense, but... PEBCAK.

"Video stream was lost" means the camera is dropping signal. Log into the camera firmware, export the log for all events to a CSV and inspect for "Off-line Event" or any no signal event - indicators that the camera connection to the router is unstable. That's the first thing to check.