In one of my recent updates, I changed the default GUI configurations to use the notbountiesadmin command. I was alerted earlier today that this is not compatible with the completion commands for the bedrock-gui. The {player} placeholder is used for the player you click in the menu, so I added a {viewer} placeholder for the player that is using the GUI.

How to fix setting bounties for bedrock players:
Open your bedrock-gui.yml file.
If you have not made any changes to your file, delete it, and reload the plugin to regenerate the config.
If you have a shortcut to find and replace, enter "notbountiesadmin {player}" to find, and "notbountiesadmin {viewer}" to replace. Otherwise, you only need to replace it in 4 areas:
1. The player-button-commands in the bounty-gui section
2. The player-button-commands in the set-bounty section
3. The player-button-commands in the set-whitelist section (if enabled)
4. The completion-commands in the select-price section

I also commented out the whitelist button in the selection menu in the default file because whitelists are disabled by default.