For all of the members with this situation we know about, I re-imported using the procedure described earlier. So, those all do have the button back, but that was before I started this thread. We have no idea how many have not been discovered yet.
So far, there have been about 20 memberships affected by this, but none in the past 10 days or so. As I stated previously, this did not happen before I updated to CB Subs 2.0.1.
We have also been experiencing sporadic difficulties with several other components as we update those to current versions (which are compatible with J2.5), so I have been wondering if J1.5.26 might be stressed beyond its capabilities. As I also stated previously, when I updated to CB Subs 2.0.2, CB Subs crashes to WSOD, requiring a roll-back to 2.0.1. There is obviously a conflict introduced with this new update.
I've been trying to convince this client to upgrade to J2.5 since the beginning of the year and we are working on that now, but it's not planned until the first of next year. Hopefully, with the migration to J2.5, some of these issues will settle down. At this point, I think this will take much more time to diagnose than it is worth and I don't want to consume any more of your time than I already have.
I'll continue with it as it is and handle any new instances manually as I have been until the migration. If it continues after the migration, I'll have to revisit this as a support issue.
Thank you for your assistance.