If a Conversation Timeline says "Routed to <Inbox> because <Agent> had a conflicting offer," this usually happens when the Agent in question sees a notification banner to accept or decline a request at the same time another Agent or routing event is attempting to route another request them.
Keep in mind that an Agent can only be offered one Customer request at a time. Attempting to route more than one at the same time to an Agent would cause the conflicting offer error.
If a Team Manager is attempting to manually re-assign Conversations, they should wait at least 30 seconds between reassigning different Conversations to avoid the conflicting offer error.