Adobe LR Classic unable to utulize PC ressources

Hey, I have run into an weird bug. Using eitehr 13.2 or 13.3, HDR, HDR-Pano & Pano Previews and Merge cannot utulize my system anymore an take ages. Taskmanger is reporting not even 10% Utilization. 

I already tried reinstalling LR and going back to 13.2. I also did a reinstall and rollback on my NVIDIA GRD drivers.  Even when turning of HW-Acceleration LR does not use the CPU or GPU at all.