For a query with a LIMIT, the coordinator cancels remote fragments once the limit has been reached. This can happen before the backends have successfully sent a profile update, and any subsequent updates are ignored because the query is cancelled, so the complete profile is never fleshed out.
When the query is an INSERT, it is possible that a race in the coordinator code handling the remote profiles leads to a crash. This only seems to happen occasionally with large clusters (as reported), and we haven't been able to reproduce this internally yet.
We should probably wait until all backends have completed one way or the other before tearing down a query completely.
A workaround is to remove the LIMIT.