had nothing but trouble after the update to 5.1.1, including,
Garbled/useless microphone when making calls (only speaker/headset/bluetooth worked),
Notifications going crazy with no way to turn them off,
No "true silence" mode without shutting down everything including alarms,
Ringtone for phone continuing to ring after Dismissing calls (required reboot to silence),
Many apps no longer worked,
Battery charging icon not animated,
Battery circuit very picky...only select chargers and cables worked after upgrade when prior, everything worked,
So many little annoyances, combined with huge ones (it's a PHONE and I can't use it for calls???) made me seek a way to rollback, which I did.
I have a OnePlus One, and I think the issues are centered in the way the OPO works with Cyanogen Mod 12. I think CM 11 was better, and KitKat was flawless on the OPO. After the upgrades to 12 and Lollipop the phone was essentially useless to me.
After rolling back, everything works again and I'm happy. I will never upgrade this phone. Also, I will never buy another OnePlus phone. The lack of rapid customer service is too much of a problem.
Dave