The server started to randomly crash after a few minutes/hours due to a Null Pointer Exception on the getSaplingGen() method from SaplingListener.
The bug has been reproduced several times with and without players online, also I was able to grow Oak Saplings without any crash. I also saw someone with the same problem on OTG's CurseForge project page.

Each time a crash report is generated but it doesn't tell which sapling is causing the crash nor it's location in the world. The log doesn't tells much more.
crash-2018-06-09_16.28.49-server.txt or https://pastebin.com/LTpHbNXp

Hey rs4-06, what kind of OTG world are you using? Is it Biome Bundle or did you create one yourself? Did you edit any of the sapling settings in the biome configs?

Hi, thank you for the quick reply. I used the latest version of Biome Bundle with the default config.

Using Biome Bundle on 1.12.2, this happened to our server as well. What we suspect is Acacia saplings, though this could be an edge case. Said sapling was planted in a Magical Forest, which was formerly Tundra (changed via RFTools' Terraformer), according to OTG it's supposed to be DrylandsEdge1 / *2

Should (hopefully) be fixed with v7_r25.