SERVER-71755 added code to insert the shard metadata along with the database metadata and the placement history in a transaction as part of PM-1939, this fixes addShard not registering all the databases if there is a failure in the middle of the write operation, and allows a stable timestamp to get the necessary metadata for change streams, however, a replica set with too many databases could have a similar problem as the one described in SERVER-58433, where we reach the limits of the WiredTiger cache size for a transaction.

SERVER-79160 adds to that transaction the collections present in the shard, making this problem more probable. We should batch the request in several transactions to mitigate this, until we have a fully reliable addShard which should come in PM-2050.