Bad performance (Low FPS) with World Update 3 and new London photogrammetry - possible memory leaks

So what puzzles me with London is there are clearly graphical glitches in the scenery - the Thames has these strange reflective spot which appears to be windows to scenery rendered below the London photogrammetry.

It wouldn’t suprise me if it wasn’t just trees they were rendering twice but a completely new layer which should be culled from view.