The upgrade NPCs for mythic gear won't let you update an item with this addon enabled. It will tell me I that the addon is interfering when I attempt to upgrade and then just not upgrade the item. I have to disable it every time I want to use this in-game feature. This issue has been ongoing for several months, as I constantly had to disable the addon in Korthia. There is no LUA error itself, just a popup that I need to disable the handynotes shadowlands treasures addon to properly upgrade my gear. With the addon disabled, I don't encounter any issues with this.

Also lately, it also makes it so that I can't auto-populate mythic keystone information into the LFG dungeon group finder. It will populate everything but the key level. I found this report from my buggrabber.

2x [ADDON_ACTION_BLOCKED] AddOn 'HandyNotes_ShadowlandsTreasures' tried to call the protected function 'SetEntryTitle()'.
[string "@!BugGrabber\BugGrabber.lua"]:519: in function <!BugGrabber\BugGrabber.lua:519>
[string "=[C]"]: in function SetEntryTitle' [string "@FrameXML\LFGList.lua"]:1144: in function LFGListEntryCreation_SetTitleFromActivityInfo'
[string "@FrameXML\LFGList.lua"]:1013: in function LFGListEntryCreation_OnPlayStyleSelected' [string "@FrameXML\LFGList.lua"]:720: in function LFGListEntryCreation_Select'
[string "@FrameXML\LFGList.lua"]:645: in function `LFGListEntryCreation_Show'
[string "@FrameXML\LFGList.lua"]:579: in function <FrameXML\LFGList.lua:567>

Thank you for your attention to this issue. Have a nice day.

So, this gets reported but has never actually happened to me. I'm going to make a speculative change, but I can't really tell whether or not it'll actually help...

Okay: either wait for a full release, or try installing the alpha. Either way, let me know if this helps.

Lacking an update, I'll assume this helped. Reopen the issue if you still see the problem.