i turned off all other addons to make sure it was an issue with bagbrother. when i click the character icon thats supposed to let u view all ur other characters inventories, it doesnt work. i verified that i had bagbrother on as well after turning all other addons off and it still didnt work. also tried clearing cache after that and still didnt work. the addon is up-to-date as well as of the most recent update on wow-up 1 month ago for 9.1.3

Same issue here, BugSack output below:

1x ...\Wildpants\libs\Sushi-3.1-4\classes\drops\Dropdown.lua:136: Invalid data provided for `:SetBackdrop`

[string "=[C]"]: in function `assert'
[string "@Bagnon\common\Wildpants\libs\Sushi-3.1-4\classes\drops\Dropdown.lua"]:136: in function `SetBackdrop'
[string "@Bagnon\common\Wildpants\libs\Sushi-3.1-4\classes\drops\Dropdown.lua"]:48: in function `New'
[string "@Bagnon\common\Wildpants\libs\Sushi-3.1-4\classes\drops\Dropdown.lua"]:57: in function `Toggle'
[string "@Bagnon\common\Wildpants\classes\ownerSelector.lua"]:32: in function <...ns\Bagnon\common\Wildpants\classes\ownerSelector.lua:30>

Locals:
(*temporary) = false
(*temporary) = "Invalid data provided for `:SetBackdrop`"

Note: As a workaround until this is fixed, you can use these commands to open bank/guild bank/void storage respectively:

/bagnon bank
/bagnon guild
/bagnon vault

i forgot to mention what version this is for. this issue is for the retail version. the tbc one works fine. idk about the classic one tho

I'm having the same issue exact same. very strange indeed because ive used the mods for a decade and have never encountered this issue.

thank you for the fix brother.

I posted a fix for retail on curseforge. Here is a link to the post https://www.curseforge.com/wow/addons/bagnon?comment=8774

+1 confirming it works (used Nevicar's pastebin in the reply for convenience).
thank you so much!