PE13: Slow and bumpy playing of unrendered files

Dear all,

I recently had to change to a new computer and am facing problems I didn't have before though this laptop has a faster CPU than the one before (i5-6200U/2.30 Ghz). Simple video files are being played sometimes slow and bumpy. After rendering everything is fine, but I only need to do a tiny change in the clip (a cut, changing the opacity, changing the lenght, etc.), and again the problem is back. I didn't find any setting yet that could change it. PE13 is running here on Windows 10.

I will be grateful for all suggestions!

Thanks & Regards