As reported here:
https://forums.adobe.com/thread/2620272

Steps to Reproduce Bug:
1. Import a clip and then make a low res pro res proxy.
2. Apply Technical LUT to a clip and then put it on a timeline.
3. Change anything from sequence settings (framerate, size, etc).

Results:
Visible gamma shift between play and pause state.

Expected Results:
No gamma shift at all.

Workaround:
Toggle proxies off and then enable proxies again.

System Info:
Version: Premiere Pro 13.1.2
OS: Windows 10 1809
GPU: Nvidia GTX 1080 Ti
Drivers: Latest (430.39)