How do I repeat "Drug Shootout" at Braddock Farm or Weed Farm?

I've done it the first time but I can't trigger the event 2-3 weeks later. Several times I tried raiding it again but the farmers don't come back.

• Wikia says it's probably a unique event: http://gta.wikia.com/Braddock_Farm
• IGN says it's available every tuesday with any character from the 2nd time onwards: http://www.ign.com/wikis/gta-5/Raiding_The_Weed_Farm!
• Someone claims it used to work before a patch fix: http://gtaforums.com/topic/605948-weed-farm-not-respawning/#entry1064050226

This encounter was intended to be a recurring event where, while playing as Trevor, you would be able to return to the farm after seven in-game days. It appears one of the Rockstar's updates broke this system, rendering the encounter into a one-time appearance.

According to the farm's Wikia page:

Although the game prompts the player to return in a week or so to steal any future earnings, this Random Event now no longer repeats following a software patch.

It's unclear what patch broke the encounter, but it explains why some forum users were able to repeat the event but are no longer able to do so.