Just a word of warning, I just came upon this glitch with the new experimental branch released 9/27/19. I found a crashed ship. My current ship is an A-Class Explorer 38/12 and the crashed ship is an S-Class Hauler 48/8.

I claimed the hauler to add to my ship collection and when I went back to my other ship, I noticed that suddenly it had the same number of tech slots, and they were all damaged exactly like the crashed ship. The tech slots of the damaged ship were copied over onto my other ship. I not only lost 4 tech slots, but they're all damaged.

Thankfully I was able to revert to my save, before claiming the ship - so no permanent harm done. After the reload, I experimented by calling my other ship and then tried reclaiming the crashed ship. The exact same error happened.

So BEWARE of claiming a crashed ship with this experimental branch. I'm reverting to the latest release version and trying again to claim that ship and see what happens. The download just finished, so I'll post my results here.

I also sent a bug report and saved game file to Hello Games, so hopefully this will be fixed ASAP.

EDIT: I just checked and the bug does NOT appear in the release version, so feel free to claim crashed ships in that version of the game., I may claim the ship in the release version and then re-do the experimental branch after bring them all back to my freighter.

Strange what you report here because since NEXT/VISIONS once you exchange or swap ships you cannot interact any longer with your old ship, HG has made it so to avoid exploits. I cannot reproduce it in 2.12, but I don't play Experimental .
Also once you swap / exchange ships the game will create an Autosave immediately, again to avoid exploits. If you want to revert you would have to load your last manual save and losing some progress.

I think OP refers to adding a ship to the collection, in which case the game switches active ships to the newly claimed one, and both ships stay accessible. Since they're both yours now.

@Velgor,

did you by chance try to reload, after you added the new ship to your collection, and then check the slots of your other ship ? Maybe it's 'just' a display bug (bad enough) ?

No, I did not try a reload since I didn't want to chance making the problem permanent. I reverted back to the release version, loaded the save before claiming the crashed ship, and tried claiming it once again. The glitch did not happen. So, it's just in the experimental branch.

In every case: Its always good to copy/backup your entire savegame folder on regular fashion, and especially when you expect problems, because the manual saves in-game are not permanent. You only risk to lose some gameplay progress when doing this.
The next higher step is to get familiar with NMS Save Editor which is able to correct many stucked situations that you may encounter in-game.

Ah, I misunderstood, assuming that you reverted to a backed up save. Thanks for the clarification.