The Voidforge system is brand new to Patch 12.0.5 and is supposed to have a knock-system for loot. This means that when you bonus roll an item, you are not supposed to be able to bonus roll again.
However, there have been multiple reports on Reddit and in Discord of players who have Bonus rolled the same item with both their bonus rolls.
Reddit Post where player got Heart of Wind trinket from Windrunner Spire twice.
Another Reddit Post where a player got tth same 2H polearm in Skyreach.
A Reddit Comment where a player got two chests from Maisara
A Discord Post where a player got two Platinum Star Bands
If you want to avoid duplicates, you may want to save your Bonus Rolls until the system is fixed. Some players have said that different keystone levels are on different loot tables, and it's unclear if this has been confirmed or not. Two players have reported duplicates on the same keystone level however.
