So, I play with KSP 1.3.1, and CKAN told me there was an update available for Interstellar Extended. I was using Interstellar Extended 1.21.8, so I went ahead and updated to 1.21.9 via CKAN. However, when I'm trying to load the game, MiniAVC tells met hat Interstellar Extended 1.21.9 is not compatible with KSP 1.3.1 and asks me to use KSP 1.4.5. In addition, the game loading hangs on:
Squad/Parts/Engine/liquidEngineLV-N/liquidEngineLV-N/nuclearEngine

...and it's not frozen, as it continues to give me loading indicators every few seconds such as "Scattering atmosphere" and "Loading more loading screens"

I also wanted to add that the Gas Chromatograph Spectrometer and Liquid Chromatograph Spectrometer are both appearing as "missing or invalid parts" when I revert back to Interstellar Extended 1.21.8

I am on Windows 7 Professional x64, by the way.