"Package installer has stopped working" after updating to COS13/Marshmallow I have a OnePlus One, never rooted or modified the OS. Today I updated the OS from YOG7DAS2K1 (COS12.1) --> ZNH0EAS26M (COS13) via OTA incremental update zip from Recovery (stock). 

I wiped cache and user data from Recovery after update.

Phone seems to be fine so far, except this:

Whenever I sideload an APK, although the installed app works fine, an error message pops up at the end.


  "Unfortunately, Package Installer has stopped"


I tried wiping cache, rebooting, reinstalling those apps, but the error appears anyway.

What seems to be the problem here?
I do not know how to reproduce this problem. It simply solved itself after changing the Cyanogen themes a few times.