Datacache too slow?

Sometimes when starting the game I get a bunch of these messages:

[2016.10.12-00.19.00:062][ 0]LogDerivedDataCache:Warning: /AppData/Local/UnrealEngine/Common/DerivedDataCache is very slow (0.50MB/s) when accessing /AppData/Local/UnrealEngine/Common/DerivedDataCache/6/5/1/TEXTURE_814DCC3DC72143F49509781513CB9855_BGRA8_CAB411E94EC793FBF927189D054F3A6__65D3D5E608D0D362A503DFABDFEFCA64811EA437.udd, consider disabling it.

what do they mean? The location is on my SSD drive so it can hardly be too slow. What can I do about this?

Thanks