Adding/removing a user from a role on a collection, particularly the root collection, could lead to a significant increase in memory use resulting in Dataverse itself failing with an out-of-memory condition. Such changes now consume much less memory.
If you have experienced out-of-memory failures in Dataverse in the past that could have been caused by this problem, you may wish to run a reindex in place to update any out-of-date information.
For more information, see #10697 and #10698.