Provide action to do a single sync for a contact and/or mark them as needing sync
Currently the incremental sync only works for contacts whose group membership has changed since 2 hours before the last sync.
It means if someone's group membership has not changed, but other data has (e.g. email taken off hold) then they never get included in sync again.
Providing a button on the contact record that could mark their cache record as todo
would, I think, include them in the next sync run.