I don't know why as I wasn't on and none of my players reported to me the situation, I assumed it happened on chunk load or during exploration.

Crash reports:

1. https://gist.github.com/05832278a34408119e88eb3443bc4608
2. https://gist.github.com/674bc65e447319e8cd2105e0b50ca4b6
3. https://gist.github.com/4361c53acbb565921df435b1f72cbf6e
4. https://gist.github.com/52baf101877912f476ca05a5b9cbae9b
5. https://gist.github.com/de9852941ac34ca511c75b2f7aac411d
6. https://gist.github.com/399d51eb198083546bba9f6f80601a5d
7. https://gist.github.com/8f9266ba378ad06b4bf405cedd5b1e38
8. https://gist.github.com/28ea67554119d3f47a4d8a0d6a7a5328

fml logs (1 for 1 to the crash reports above):

1. https://gist.github.com/bd50ca3040e99e74a893b62be7294d3f
2. https://gist.github.com/17136fe3789268a8df7e707bf5bb9346
3. https://gist.github.com/a597880317c78e714189d330568a0667
4. https://gist.github.com/ff2a548ff7c5bb62c5f0ccb584d82fe3
5. https://gist.github.com/a95cea3c8a46006d902dfd9dbe0b608e
6. https://gist.github.com/25ace6d1c4e1588ba14a8d84c43c4cfe
7. https://gist.github.com/20395f3c48b140ec86ff8255ebac710e
8. https://gist.github.com/e3aa240427c20ea64ae02f79a597e773

and two extra fml logs without accompanying crash reports:

1. https://gist.github.com/a4cba9ac7da1ec4ffed34e0dfe555d29
2. https://gist.github.com/9a1730f2f713f4de9d436a1b302eba27

will cross post this to Biomes O' Plenty as they appear to be implicated.

Thanks for reporting! I'll look into this and see if I can restore BOP compatibility.