I do agree with you. Usually, closing the VAB and returning solves the issue.
Maybe not related, it seems the game becomes more and more laggy, until becoming not usable at all after this bug.
Best option is to close the game and start again.
Welcome Aboard.
Just joined the forum, but I had a good time in KSP1, and a little in KSP2.
Missing a science mode also! I feel like it helps in knowing the various parts. All at once is too much.