This was my first time running into this bug, but maybe it's not new.
• I edited a variant option title. (Changed it from “Add Additional…” to “Additional…”)
• It re-added 45 variant combinations I had deleted.
• It wouldn’t let me delete them and it wouldn’t let me save my changes— it said I had duplicate sku’s.
• I tried to edit the sku’s — couldn’t do that either.
• I exited out of everything, logged out, logged back in, closed the browser, reopened... same results no matter what I did.
I was going to have to delete the whole variant option and manually reenter all 155 prices and sku’s just because I wanted to take a word off the option title. Thankfully I thought to open it in Classic Editor and I fixed the title in 5 seconds without it re-adding the 45 deleted variants or changing the sku’s or any of that mess.
It was baffling.