crap. sorry. :( I only tested one match as I was focused on getting the actual fix implemented ASAP.
Have seen a bunch of posts about this, and since this reasoning behind this doesn't reveal any great secrets and I think players generally appreciate some insight into the process and since it's entirely my fault and therefore I won't seem to throwing anyone else under the bus...
Anyway, it's a bug related to the new Artifacts. Basically, unlike every other skin in the game, Artifacts aren't a single skin; they are three - blade, power source, and theme. Making that system work in parallel alongside regular heirlooms - which are a single skin - was a unique challenge. And in testing, there were quite a lot of bugs - most (probably all) of which came from the DEV environment being different. Trying to split the difference between testing the flow as players would experience and also not making every artist who wanted to make a change have to buy each component one-by-one. And so there were quite a lot of bugs where testers would get broken Artifact configurations that wouldn't work and which would crash the game. I thought this was only likely in DEV, but I also didn't want a brand new feature to be buggy at launch, so I made the system basically go through and check that your artifact configurations were always valid. This was important for testing in DEV, but we had enough issues that I thought it was prudent to have those same checks run in Production.
Unfortunately, that validation process introduced this bug *for players who do not own the Artifact,* which I definitely didn't test enough, because I was focused on making sure the new thing worked right and missed doing enough regression on the old thing also working right.
So for players who own an heirloom - but who do not own the Artifact dagger (and I promise this wasn't some weird ploy to try to force you to get the Artifact...) - the system incorrectly identifies a mismatch when you equip an heirloom. And it "resets" it ... by equipping Fists.
The fix was simple enough - only validate the Artifact configuration if a player actually owns the Artifact. And I believe the fix should go out "soon" - like, this is not staying broken until 21.1 or anything.
I've worked on this game for 3-1/2 years and every release I'm reminded of the incredible complexity of game systems and how things are so obvious - *in hindsight* - that I should have checked, tested, verified, etc. And I try to remember those things the next time I build something new. I'm sorry I broke your heirlooms. I hope my story about why makes it at least a tiny bit better...