Increasing Modifier Tier of certain Haunted Modifiers causes them to break

Putting the T4 Poison on Hit haunted modifier on a slot with +1 to Modifier Tier causes it to break, instead turning into a T2 blank modifier.

Inside the map, they are listed as Peasant-Haunted but don't seem to do anything, and certainly don't poison on hit.

Can confirm. T4 poison on hit on +1 mod turns into T2 blank modifier.