Local elections: Why has Labour lost seats?

Labour has suffered a net loss of council seats - starting from the low base of 2015 in many cases. The Conservatives have lost more than 10 times as many councillors, but what is remarkable is that the main party of opposition - around the mid-term of a not-very-popular government - has not made net gains. It seems reasonable to assume that some votes have been lost by Labour in Leave areas because - as the leader of Sunderland City Council Graeme Miller has said - the party hasn't decisively ruled out another referendum. (It has retained it as an option, if the Conservatives are unwilling to change their deal).