Just an FYI,
Same thing happened to me. First, I noticed the fps was about 1/2 normal on whatever files I tried…even started getting Fab console errors… Seemed like whatever I tried, (eg., reinstall, uninstall and new install, system restore, etc.,) things deteriorated.
Ultimately, my system became unstable.
I had dug myself quite a hole and had had enough.
I keep a recently cloned system hdd ready to go on an eSATA connection.
I simply changed the boot priority, rebooted and recloned with a stable system hdd.
Once again, I downloaded and installed 18.104.22.168.
This time, no problems. The conversion times are even a bit faster than the previous beta.
I can only guess I had a corrupt download/install although there were no obvious clues to this.
I firmly believed this was just a fluke and was not reproducible in any respect.
You’re the first user, besides myself, that has mentioned the slow mpeg-4 conversion time.