Rejected events from /get_missing_events never reconcile

*This issue was originally created by [**@MyYuan**](https://github.com/MyYuan) at .*

Two dendrites were built, and room_one was created on server2. Thousands of users on server1 and server2 joined the room_one and chatted very actively in the room. After running for a period of time, the data of the two servers was out of sync and an error was reported. Message as follows:

Is there any way to quickly solve the data synchronization of dual servers? Currently, the chat content of server1 and server2 in the same room has been completely isolated

Start by reproducing the two-Dendrite federation scenario described in the issue, with room_one active across server1 and server2. Inspect the /get_missing_events path and the attached error report to determine why rejected events remain unreconciled. Done means the room's events can synchronize again between both servers without isolation.

Written by the indexing model from the issue text.