Autosave and exporting aren't related at all, other than perhaps autosave might be paused while PD is busy producing the video.
The obvious choice to avoid losing work since you've noticed an issue with autosave would be to make sure you manually save your project frequently, and certainly before clicking on the Export button.
I just did a test with V21.5.3107 that came out on July 12, and the autosave is working normally on my system with the timer set to every 3 minutes:
As for the exporting issue, what happens if you produce to a different profile? For example, try uising the Profile Analyzer and produce to Best Matched Format? If that doesn't work, try unchecking the
Fast video rendering technology: box.
You might have an issue with hardware encoding and may also need to uncheck Enable hardware decoding from Preferences | Hardware Acceleration