Serious error occurred after edit changes

Hi,

In the middle of my editing the program told me a serious error occured. I had just applied Morph Cut transitions to clips. Which might have caused it, but I had done so earlier in the timeline without errors.

INFORMATION:

macOS High Sierra Version 10.13.6

Storage available: 50GB (is this not enough maybe?)

Processor: 2.5 GHz Intel Core i7

Memory: 16GB 1600 MHz DDR3

Graphics: AMD Radeon R9 M370X 2048 MB / Intel Iris Pro 1536 MB

Most recent Premiere Pro version (I updated immediatley after error, and it still came up in new version)

Source footage: Editing with 4k h.264 proxies on 1920x1080 timeline, but original is 4k .mp4 (from sony a7rii). I have been editing this kind of footage for a year in PP.

Problem occured a few clicks after applying Morph Cut transitions. Now it occurs if I just open the project and wait a while without doing anything (a minute maybe).

This does not happen when I open older projects.

WHAT I HAVE TRIED SO FAR, TO NO AVAIL:

- Creating new project and importing the broken one — still error

- Resetting preferences of Premiere Pro

Thank you, I have a deadline tomorrow, of course...