Notes collaboration starts normally, but soon fails

Introduction:

I'm hoping to use notes to help my students since Notes allows drawing with the pencil and collaboration allows real time viewing of changes. I've decided to try this with some students with an Ipad and pencil. It's important that we be able to use the drawing capability here so I can see the issues that they run into when doing their work.

Situation:

I have successfully started collaborating several times. I make a new note, allow my student to collaborate and they can see my writing and drawing in real time. I too can see their drawing for about 3 minutes. After that short period, I see no more updates and changes on their part. They can continue to see my changes and drawings.

Specs, etc:

We're using Ipads with fully updates OS. We both have free memory on our Icloud accounts. We both have Notes activated on Icloud. I'm using an Ipad air A2588, and I don't know their specific Ipad air model.