In the process of updating the thoqqua I modified (and deleted) some code before understanding how it all works. Currently thoqquas no longer create lava, but turn stone directly into hot magma. It might be a good idea to re-instate the old code relating to turning stone to lava (and back again when the thoqqua dies or despawns).

Yes, I forgetfully duplicated my own issue in a project I've been primary coder for... (need an embarrassed emoji here...).