Lava cauldrons flicker regularly in Dimension of the Machine's hub

[Macil]

In the Dimension of the Machine level hub, in the left and right rooms with the main level portals, the central lava cauldron regularly flickers, seeming to become very bright for maybe a single frame. If you noclip into it, you can see that the flickers seem to be caused by the light of a lava fireball that appears occasionally inside the cauldron before immediately disappearing.

qss-flicker.webm

This issue does not exist in the 2021 rerelease or QuakeSpasm (neither the flicker or any kind of lava fireball appears). This issue does exist in vkQuake. This issue still happens the same way even if I try "host_maxfps 72" or "pr_checkextension 0".

There are other lava cauldrons in the level hub that do regularly spawn normal lava fireballs that cast light and fly into the air and back down. I think the two problem lava cauldrons have fireballs that spawn too low and collide immediately into the level geometry (in all ports and the 2021 rerelease), and in QSS they show up for a moment before being destroyed.