One more thing that absolutely has to be tuned:
In /home/user/.config/tracker/tracker.cfg:

# Minimizes memory use at the expense of indexing speed
LowMemoryMode=false ===> true
# Sets the indexing speed (0->20, where 20=slowest speed)
Throttle=0 ===> 15

And then restart the Tracker. This seems to fix the Camera, so that you can make more than one photo without delays and sluggishness. Although I have not yet tried how camera works after a few days of uptime with this change.