I seem to get this went logging in or hitting a load screen such as after hearthing.

77x RearrangePetTab\RearrangePetTab-1.2.lua:94: bad argument #1 to 'unpack' (table expected, got nil)
[string "=[C]"]: in function unpack' [string "@RearrangePetTab\RearrangePetTab-1.2.lua"]:94: in function ?'
[string "@RearrangePetTab\RearrangePetTab-1.2.lua"]:216: in function <RearrangePetTab\RearrangePetTab.lua:214>

Locals:
(*temporary) = nil
(*temporary) = "table expected, got nil"

Seems like an issue with ElvUI where the frame I intended to move/create has no size.
Can you try the latest RearrangePetTab.lua in the repo? If that fixes it, I'll push a new release.

That seems to have fixed it! Thank you!