Its hard to tell from the last image but I think your sub-assembly has become corrupted and I would think the easiest fix would be to try restore your highest version from the "OldVersions" folder
If the article is a little tough to follow then perhaps this video will help. Just backup your original file before you over write it with one of the old versions. You are likely to lose some of your changes but maybe it is only a little and better than losing the whole file. If you had checked the file into Vault you could do a get of a older version from Vault if you had not saved since your last check-out.
If this solves your issue please mark this posting with the "ACCEPT SOLUTION".
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