Hi Alarob,

By design, each time a repeating action is completed in OmniFocus it
spawns a new action. So what I think that happens in your case (what I do very often accidentally as well) is that you check a repeating task, and uncheck it at some point. Therefore Omnifocus will automatically create a duplicate of you repeating task.

I hope that in the future, Omnifocus will automatically delete the
spawned action when un-marking a task that has been already marked
complete. That would fix this problem.