Meta-crafted weapon rolls impossible mod

https://imgur.com/a/hXLpeYj

Attempting to craft a +3 Fire skills staff; despite having Cannot Roll Caster mods it rolled a (what I believe to be) caster mod of non-ailment chaos damage over time multiplier.

Ruined my craft and cost me the exalts I had finally saved up.

Can’t say if that’s a bug or not but I think caustic arrow users would disagree it’s a caster mod only.

Fair enough, but I have Cannot Roll Attack Modifiers as well, so it should be covered between the two of them. I can't find anywhere what type of mod that is so I also am not sure if it is a bug or not

According to the internal tags it is neither caster nor attack, just like mana and +gem mods are neither. Looking at the tags is not much of an explanation though, it just confirms that all tiers of the mod are not tagged as either, so it isn't an obvious error/bug. I would guess that it is intentional, because like mark1030 wrote it has use for both caster and attack skills, but I don't know of any official comment about that specific mod.