Due to the 2.0.33 change to remove a lot of unused sprites a significant number of mods broke for that update, and so I've avoided updating to that experimental version until all the affected mods are patched. But this means that re-enabling the LDS cooling re-introduced this bug, and doubly so as the mod update isn't set to require 2.0.33 either.

Not sure what the best way to handle it is, but I do need to manually downgrade and ignore updates for this mod for now as a result

Hm.... 2.0.33 ist still not stable... I don't know. Probably it's best to downgrade Hot metals and update it together with Factorio once 2.0.33 is stable. I don't really wan't to go back again. I should have waited or add a minimum Factorio version. I forgot about that to be honest.