First I used a Thaumcraft Wand or Sceptre that is not on the Creative Tab as quest icon:
moving quests in the designer would drag the image (not the location) of all lower / right (higher indexed?) quests with it, along with the source of their link lines. The others were unmoved in the .json and had to be clicked in real position. The icons and links remained displaced even through save/load and re-launch of minecraft.
This was accompanied by log spam of GL buffer overflow.

The same wands used in tasks (retrieval or crafting):
Crashes the client at screen updating caused by Thaumcraft wand drawing immediately upon flipping to that task page.

In particular: silver capped greatwood wand, copper capped wooden wand, and ichorium adorned ichorcloth strapped sceptre were in use. Each and all exhibit this behavior, removing them all (by editing the backing json) fixed it.

I'm currently only doing support for BQ3 builds in 1.12.2 sorry.