Media Encoder taking a long time to mux H.264 vide and audio

I am having a similar problem. Media Encoder as well as Premiere Pro are getting very slow at random even though no additional programs are running at the same time, the hardware is strong enough (Macbook Pro 2022, M2, 16GB RAM) and the render destination is set on the itnernal SSD. 

In MediaEncoder this results in render times that are ridicioulsy high (8 hrs or similar) and in Premiere Pro nothing really works and just stands still.

I checked the usual troubleshooting steps like deleting unsued media cache, checking that there is enough space on the internal and external SSD drives in use, updating the programs to the newest version etc.

Nothing works, and its getting in the way of being able to handling the workload on my table. 

Would appreciate some ideas in where the problem might be!!