If the reported message is issued, the "isSnapshot" flag must have been set to true on the "update" or "smartUpdate" call,
which is not allowed for an UPDATE (or DELETE) event;
This is a check that you can put before the call, so as to force false in these cases.

Note that the first call with "isSnapshot" set to false terminates the snapshot;
subsequent calls with with "isSnapshot" set to true are managed as real-time updates.