The appservice-slack and mautrix-slack components are both enabled and use the same bot username ({{ matrix_mautrix_slack_appservice_bot_username }}), as per their default configuration, which causes a conflcit.
To resolve the conflict, make one of these components use a different username.
Consider either changing `matrix_mautrix_slack_appservice_bot_username` (the bot username for the mautrix-slack component) or `matrix_appservice_slack_bot_name` (the bot username for the appservice-slack component).
We recommend that you change the username for the newly-added (and yet unused) component.