• Modpack: FTB Daybreaker Horizons
• Setup: Default Firework recipie (Paper+Gunpowder) in Crafter Tier 3
• Crash after putting Gunpowder in by hand (paper is already in it)
• ! Random (worked before and wasn't able to reproduce it...)
• Error log: http://pastebin.com/ZcXvUFz5

I cannot reproduce this in rftools 3.31 but I also did fix something there so it is possible this bug is solved

Okay was now able to reproduce it.
Have made an instance with only RFtools 3.31, mcjtylib 1.3.0, CoFHCore and ExtraUtilities for PowerGen.

Both times I placed a crafter and set the recipie for the rocket,
When I power it and then put the items in it works.
When I first put the Items in and then Power it it crashes.

Same crash but still here the Crash Report:
http://pastebin.com/cxBiUju9

Aha, now I could reproduce this.

Next version of RFTools will have a workaround for this. Not sure what causes the crash though but at least the crash will be gone