Can't process more than 3 videos

Many versions ago, I could load up many videos at once, say 6-8, let the program run over night, and they would all be done the next day. For the last several months, with the various new versions that have come out, if I load more than 3 videos, only the first 3 will process and the others will fail. In the output area at the bottom of the GUI, each video beyond 3 shows a red x with the word “failed”.

I tried setting the" Max Processes" in settings to various numbers but that had no effect. It apparently just determines the number of videos that process simultaneously.

Is there now is a maximum number of videos that can be loaded and processed? Or am I dong something wrong?