Premiere last version v14.5 too slow to work with

hello!

I assume the last update is doing something weird because all of the sudden Premiere is acting so so slow compared to what I was used to, especially the playback !

Right before the latest update, everything was just fine! I edited about 40 videos of 1 min each, dealing as usual with 4K and HD 25fps files coming from my Sony A7III. Nothing was wrong.

Now I have basically the same workflow, just different outcome as I aim to create a 20min video. Yet using the same type of files, when I uncecked the video levels, audio rolls quite smootly but once I enable one little clip to play with the audio, it's incredibly slow!

I cleared media cache and tried all other tips and tricks to speed up but no luck yet.

This drives me crazy! Please help!

My specs are the following:

PREMIERE PRO V14.5

macOS Catalina 10.15.7

Mac Pro late 2013

Processor 2,7 GHz 12-Core Intel Xeon E5

Memory 128 GB 1066 MHz DDR3

Startup disk Machintosh HD

Graphics AMD FirePro D300 2G

Thank you in advance!