Abyss fissure chance mod only rolls once per zone

Bug Report ID: #478221264

I'm using a mace with the abyss mod "Fissure skills have a x% chance to create an additional fissure" with Ahn's Citadel on Shield wall.

Normally this combination does nothing, but sometimes when entering a map I will permanently create two fissures instead of one on every attack. It seems to be rolling the chance per zone instead of per attack.

The report ID is in a map where the duplication is stuck.

Also removing the weapon causes the duplication to go away, and re-equipping it will bring it back without leaving zone.