Do you have any regular servers which are showing the same issues? I don't know what special plug-ins Dark Gaming uses; if it uses anything but just the vanilla server functionality, it is not necessarily a valid bug report.
Vanilla TerrariaServer.exe servers function totally as intended.
TShock servers have had SERIOUS issues as of I think 1.4.3 (not 100%, earliest I can find us recording this is December 2021, a short while after 1.4.3) where quite simply any modifications made to the player file won't save (on TShock servers).
As far as I'm aware this is a result of TShock "using some kind of exploit" to modify the player file, as such I doubt this is a valid bug report, I don't see anything in any patch notes talking about Relogic having vehement hatred of multiplayer servers or anything silly like that, rather the way tshock worked was simply sorta backwards due to terraria being.... well, old.
I will contact one of my friends who is an experienced TShock dev and plugin creator asap to get a more proper description and post it, or just edit it into this comment in the scenario this thread is locked due to it being an invalid report.
Small Edit: I remember now after digging into it and talking with a few others, it seems to be that TShock is stuck in SSC mode for some reason as of 1.4.3 (meaning the client would stop saving changes made to the player after they left, thus reverting the character back to how it was before leaving), will update with any more small details I find, but I'm certain this isn't something ReLogic is going to concern themselves with, if I had to guess I'd assume ReLogic implemented some kind of anti-cheat where the player cannot be forced in and out of SSC modes while the player is in-game?? Or something like that haha
Proper Edit & Explanation: "When SSC is on, the player won't be saved no matter what" - Durtle, a DG & TShock Plugin Dev
This seemingly only affects servers with the Dimensions plugin, more reason this bug report is likely not to be handled properly by ReLogic