When using WIT and looking at specific items which don't seem to be related, other than the fact they're modded blocks, WIT outputs the proper information but also the following java error :

java.lang.ArrayIndexOutOfBoundsException

As seen below (with no modules enabled)

Version info:

• Minecraft 1.10.2
• WIT 1.9.4-1.0.23-44

Other mods:

• ConquestReforged 2.1.3-mc1.10.2 (error occurs on blocks from this mod)
• OptiFine 1.10.2_HD_U_E3
• JourneyMap 1.10.2-5.4.5

Have a crash report or log files?

It doesn't generate any (logged) errors, only the message displayed within the tooltip itself. Any debugging options I could follow to generate something?

I don't remember the 1.9/1.10 WIT code too well at this point, but this kind of error is typically the fault of the other mod. All I'm doing is asking the block for its name and catching the error the other mod generates.

WIT-1.12-1.0.25-44

I appear to have this same crash with a mod called Ferdinand's Flowers (but in 1.12.2):
crash-2018-02-09_12.03.53-client.txt

Let me know if I should report it to them instead of yourself.