Clips get pixelated after making adjustments

[Michael.Eleven]

Hi there!

I use the most recent version of PP. I have a project with different source material (25 & 30 fps, full HD and 4k), various titles and graphics. The output is set to 30 fps full HD.

Everything works flawlessly. I can do basic adjustments to the clips. But as soon as I want to apply stuff from the "creative" tab, the corresponding clip becomes totally pixelated. 

And that is in preview AND after rendering.

My hardware: i5 3570k @ 4.3 GHz

16 GB CL9 RAM

GTX 1070 8GB VRAM

All on SSD

Why is that? 

Thx a lot in advance!