FPS drastically reduced after entering large cities

I installed latest nightly and after entering Balmora, or Vivec the FPS fell to roughly 0.20 (right after entering the cell, both after traveling and by foot) making the game absolutely unplayable. Everything gets back to normal in menumode or outside the cities. According the performace graph it seems the physics calculations are here to blame (see screenshot). Small settlements seem to be okay, giving about 30 in Physics. Happens both with loaded and new game. This wasn't happening with 0.38 stable.

(RM-3237 from redmine: created on 2016-03-06 by Lord Berandas, , closed on 2017-01-01 by nobody, duplicates #3355 (closed))

Attachments: openmw.log