Try a binary search and figure out which mod is causing it. So disable half of the mods, see if issue is still there, if yes disable half again etc etc until you find the mod that's causing the issue.
I would recommend you test with only these mods installed: distant horizons, sodium, fabric api and iris If the issue occurs with only these mods, then you can be absolutely sure it is not your mod collection causing the issue, and is actually just distant horizons by itself
it shouldn't take you too long to figure out, and this is one of the problems you'll run into when using beta versions of mods, like shader support for distant horizons. You might want to post your mod list in here, in case someone comes along later that knows more about mod compatibility, but for now the best you can do is try figuring it out yourself
it's working now. idk what fixed it but i'll try to pinpoint what did. maybe this issue is just inconsistent and happens sometimes idk. it works now but takes a few seconds to start loading LODs after switching dimension
i looks inconsistent i guess. sometimes it takes a whole minute to start generating LODs again and sometimes instantly and sometimes never until the game crashes. well then, i'll just ignore this issue