Pretty straightforward as the title says. Works fine in singleplayer for whatever reason, just not on the server.

We believe it may be to do either with Unearthed saying its both version 1.3.0 and 1.2.2 and/or to do with the DynamicTrees Mod which is a part of our modpack, but we're honestly not sure hence the bug report.
We have tried previous versions of Unearthed but they result in the same bug.

Server loads and runs perfectly fine without Unearthed, but we see this mod as pretty much essential for our custom map and as such have a great deal of interest in seeing this issue resolved.

The latest full crash report can be found here: https://pastebin.com/pU2GFMTh

Thanks in advance! :)