problems saving multiple new tasks

We have been using this plugin for years and love it. But just in the past few days/weeks we are having problems adding tasks to existing sheets. I can’t think of what could have changed in wordpress to cause this.

Behavior:
Open an existing signup sheet (with existing signups).
Use the (+) button to add 1 new (empty) task at the bottom.
Fill in the information for this task.
Use the (+) button 10 times to “clone” the new task.
Change the dates for the 10 new tasks to 10 new dates.
Save.

This method has always worked in the past. Now when we save, the newly added tasks are all gone. If we add only one task, it saves the new task just fine. But if we try to add several at once, they aren’t saved.