How to avoid safety PSA:
This glitch occurs when you update a spacesuit mod that includes separate boostpacks. (A similar glitch can occur with clothing mods that are updated where parts of the outfit will go invisible. Very embarrassing when your character's private bits start popping out in public.)
To avoid these glitches:
1. Remove all spacesuits, packs, helmets, and/or clothing that the mod adds/changes.
2. Wait 48 hours UT (land on Venus for convenience) and create a new save.
3. Update the mod as normal.
4. Load the game and immediately wait 48 hours UT.
5. Create a new save.
6. Obtain and equip the updated items.
This is a good practice when updating any mod. The key is removing anything the mod is updating from being in-use in the save file. If it's equipped when you update, it'll probably glitch the save.