Factorio Forums

I'm not sure if it is Factorio or mod bug.

I'm using Factorio Extended+ family of mods.

When I'm using Rapid Belts (from the mod) when 'drawing' belts, undergrounds are not used at all. In ghost mode, there are undergrounds placed correctly, but instead of Rapid Underground, I get normal Transport Belt undeground placed.

That sounds like a mod issue which is doing a deepcopy of the transport-belt definition and does not update TransportBelt::related_underground_belt value to point into the rapid underground belt. Moving to Not a bug.