I have seen a few co-ops implode during a race.
Are you in a highly competitive group?
If so I believe that could be the reason.
! person mistakenly takes a non-135 point task or intentionally does so.
They get kicked, leaving the other member of the co-op with no way to compete.
Co-op is disbanded and disappears.
I have seen the same "co-op" show up later on with 2 of the 3 members the same.