Using the latest deobf builds ob bspkrsCore (6.14) and Treecapitator (2.0.3) I get a crash when trying to fell a tree in dev-env, crashlog.

What's probably more helpful is that the format string at that point is
[DEBUG] BlockID minecraft:log, 0 % 4 is a log.
with that sole % being what the formatter chokes on (originally initiated by this line of code, with the ModulusBlockID introducing that %).

Again, this happened in dev-env, probably does not apply to 'normal' MC, because the exception is thrown in a debug log call.

Edit: happens in normal MC with the config option allowDebugLogging=true, too.

I may have fixed this in the repo, I'll check on it though.