How coincidental. Suddenly started getting this error exporting 'iDevice 1080p".
Had exported my 48 min project two or three times, making small additions and edits before it started. Tried a few short clip test exports and got funny results, like exporting a 1:32 length clip that started AFTER the set ranges, and exporting all the way to the end (fortunately, I was within 5 min of the end.
The render files thing sounds very promising, but my question is regarding your first suggestion to
"set the Time Display to frames so you can easily locate the frame in the error message".
My Time Display is already set for "Frames", (Edit: Just checked, and was HH:MM::SS:FF, so have set for Frames) but all I have been getting is "Quicktime error -50", no time frames mentioned. No additional info available.
Will be trying your suggestions, and I also thank Nossnahojfiel for asking the question so your answer is here waiting for my search.