Random drop off of scan class Comms

we are using Ignition 7.9.9 currently and the other day we had a random situation where the default scan class just stopped communicating. I was away from the plant and driving so I was not able to get into the system myself, but the solution seemed to be that going into designer and editing one of the tags (changing nothing to the tag) and closing out, brought all of them back to reading properly, this happened about three weeks ago and hasn’t happened since. Not a big issue yet, but it will be as we use Ignition more.

Does anyone know why scan classes will randomly drop out? I have added tags since then that have default as their scan class, so I do not think I am at some limit for tags in a scan class.