I've been encountering this bug on my recent career save and I've been able to recreate it fairly consistently in my main save and in two other test saves I created. At the two test saves I've recreated the bug just by completing the contracts until the one that you have to orbit Gael, after that I put a spacecraft on low Iota orbit either using cheats or normally and on the return trip to Gael the warp bug happens.
Here's one video showing one of the attempts of recreating the bug: https://youtu.be/Y_V7TNWb-DI
And here's the log and screenshot of the in game console of one of the attempts: https://github.com/BrunoCambiano/KSP-GPP/blob/main/Desktop/Log.txt ; https://imgur.com/6w0xGxg
I've installed the GPP through CKAN and these are the mods I'm currently running:
Environmental Visual Enhancements Redux - 1.11.6.1
GPP - 1.6.8.0
GPP HighRes Clouds
GPP Textures - 4.2.1
Kopernicus - Release-70
ModularFlightIntegrator - 1.2.10.0
Module Manager - 4.2.1
The KSP version is 1.12.3, I hope I'm able to at least understand what is causing this bug so I could try to find a way to play a career campaign using GPP.