When looking/moving around a portal the screen is flickering. For some reason it only happens in the overworld for me.
Video: http://erdbeerbaerapi.tk/2019-08-05%2017-24-27.mp4

Just saw it is switching through all seasons. Looks like it is now incompatible with SereneSeasons (https://github.com/Glitchfiend/SereneSeasons)
Edit: Yes, but it is not only the visuals, but the season clock does also rotate with that

Yes, it's an issue which needs to be fixed in SereneSeasons. I've already reported it to them with details but it appears like they won't have the time to fix it:
Glitchfiend/SereneSeasons#153

Duplicate of #88

Well, until it is fixed, i remove the seasons from the server