DST] Friend can't join my server when cave exists

[Katocwatsyong]

It seems like there are quite a few others with a similar problem but I couldn't find anyone actually posted a clear solution for this

What happened is that my friend and I were playing DST on a server I'm hosting without any problem. But right after I jumped into a cave for the first time, my friend got disconnected and never can join the server again (keep getting "server not responding" msg).

I searched all possible solutions online such as re-installing, disabling mods, invite friend, etc. I figured out that my friend can only join again when I deleted the cave portion of the server by deleting "cave" folder from the cluster directory (which makes the server "forest only"). However, if I add the cave back to the server, my friend starts to get the "server not responding" msg again.

Does any1 know anything I can try? we really tried hard on this server and like to explore the cave/ruin together.

If this topic was already discussed before (probably?), a simple link to the post would be also greatly appreciated.