UK Ordinance Survey maps unknown problem

On downloading Ordinance Survey maps since the last update, all map tiles show 'Unknown Problem'

I had two Ordinance Survey maps loaded which I downloaded before the update which worked (tiles showed correctly). I got two new Ordinance Survey maps from the store and these did not display correctly. When I removed and re-downloaded the maps that were working previously, they showed the same error.

Other maps online and offline (LoMaps) seem fine

I've tried restarting locus and my phone, removing and reinstalling the locus app and deleting all the locus files - error does not go away