Meetup Keep Everyone Together function issue

Our club has been using the meetup function with “Keep Everyone Together” enabled.
We have 20+ riders of mixed abilities.
We have found on last few rides the group splits into two and then each group appear to have the “keep everyone together” working for their sub group.
So we may have 15 riders altogether and then another group of 5 that gets dropped behind.
No matter how hard people work to escape the second group they can’t.
This has happened if we use “meet up view” or not.
We have tried everyone stopping in the front group so we recombine. But once get moving again same thing happened again but to a different group of riders (with some overlap).