If JEI restarts the "ThaumicJEI Aspect Cache"-Thread gets started twice
This creates raceconditions writing to the file effectively creating invalid jsons

Screenshot of VisualVM:

Relevant extract from my Log:
Extract from Log

Pack being in used is FTB Interactions 1.1.2
Screwed up aspects-json: (txt because github ...)
thaumicjei_itemstack_aspects.txt
Full sartup log:
latest.log