I run a dedicated server and I may have a little to add here. I occasionally run into a problem where a user or multiple users will not be able to log back in getting a "server connection timed out" error. I forest-gumped my way into finding a couple of useable workarounds, but I still cannot find the root cause of the problem.
(bear in mind these work-arounds must be implemented on the server side, even though the problem appears on the client side somehow)
WorkdAround 1
Restart server
Let it get to "steam connected" phrase that shows in green
After the green connection post, it will list an update to several items. Note these item IDs or view the log later.
Stop server.
Open HeidiSQL and manually delete each of those items.
Restart server.
** This solution has worked in almost every case, with only two exceptions.
WorkAround 2 - Rollback server
I export the database as SQL every day for a backup. In two instances I have had to roll back the server to the previous day. This has resolved every instance of the problem, but results in potential content loss. This may upset players.
Stop Server
Open HeidiSQL and select your lif_1 database
open the query tab
Select "Open SQL" and load your most recent backup
Run Query
Restart Server
I would be VERY interested if anyone has found the root cause for this phenomenon, and/or a less severe workaround. An all out patch would be a godsend.