1. If you are using mods, this could easily account for such issues. Remove mods if that's the case. If still corrupt see points below.

2. If the seed you're playing on and the tames are from before more recent additions to the game, it could be that this is not possible on that seed and you'd need to make another(you can have same seed more than once in your map choices just give it a different name to be the more current one.

3. If none of that's the case, then try making a new seed(not same seed id) and seeing if the same thing happens, if not it may have been a bad seed.

4. Remote possibility to try but go to valheim in your steam library and click properties then verify local game files to make sure there wasn't a corrupt download causing the conflict.

5. If all fails, then report the bug in the bug subforum area and perhaps consider fully reinstalling the game as a last resort.