[Slurpuff]

Okay, so I cleared my bugger of all errors. I proceeded to quest in Stormheim. When I zoned into the sub-section of Stormheim, bugger popped with this error:

2x FrameXML\MainMenuBar.lua:126: Usage: GetCostForPointAtRank(rank)
[C]:: in function 'GetCostForPointAtRank'
FrameXML\MainMenuBar.lua:126: in function <FrameXML\MainMenuBar.lua:124>
...lUI\Libs\LibArtifactData-1.0\LibArtifactData-1.0-6.lua:230: in function <...lUI\Libs\LibArtifactData-1.0\LibArtifactData-1.0.lua:225>
...lUI\Libs\LibArtifactData-1.0\LibArtifactData-1.0-6.lua:289: in function <...lUI\Libs\LibArtifactData-1.0\LibArtifactData-1.0.lua:276>
...lUI\Libs\LibArtifactData-1.0\LibArtifactData-1.0-6.lua:307: in function <...lUI\Libs\LibArtifactData-1.0\LibArtifactData-1.0.lua:306>

Then, after reloading, I was able to open my artifact again. Once I completed Helheim, I was teleported out of that instance and given the same error as above. I was again unable to open the artifact.

Also, for more information, I'm a Death Knight and the artifact is Apocalypse. I didn't perform any actions to make the error trigger. I only zoned into a new area.

Edit: I can replicate this with 100 percent success. It always occurs when zoning into a new area, be it hearthstone, teleport, etc.