InUseException updating favorites

We get a few of these every day.

request-path: /portal/favorites/update
time: 11-Jan-2017 16:15:36

stack trace:

org.sakaiproject.portal.api.PortalHandlerException: org.sakaiproject.exception.InUseException id: abde1182-76de-4126-9eb1-7ba47ae5c5c4
at org.sakaiproject.portal.charon.SkinnableCharonPortal.doPost(SkinnableCharonPortal.java:1157)
caused by: org.sakaiproject.exception.InUseException id: abde1182-76de-4126-9eb1-7ba47ae5c5c4
at org.sakaiproject.user.impl.BasePreferencesService.edit(BasePreferencesService.java:298)
at org.sakaiproject.user.cover.PreferencesService.edit(PreferencesService.java:126)
at org.sakaiproject.portal.charon.handlers.FavoritesHandler.setFavoriteSiteIds(FavoritesHandler.java:103)
at org.sakaiproject.portal.charon.handlers.FavoritesHandler.doPost(FavoritesHandler.java:70)
at org.sakaiproject.portal.charon.SkinnableCharonPortal.doPost(SkinnableCharonPortal.java:1157)