The number of tasks available to process in the regatta can be severely impacted because reserved tasks and tasks that are processed multiple times occupy space normally availed for new those tasks. A couple of thoughts...
1-allow leaders or co-leaders the ability to un-reserve tasks by removing person who first reserved that task. (Although I'm certain teams have rules to guard against this issue...some team member may reserve tasks for far too much time.)
2-remove from task box, any multiple process tasks while they are being worked by team member. Once each phase is complete, let task reappear in task box for next person to tackle. This will open space for new tasks.
3-add more tasks to task box to compensate for the above anomalies.

Thanks for lending an ear!