A lot of times... More than people are willing to admit because of possible data loss... An update is not the best path. Nothing beats a clean install for smooth operation of a device. Nothing. If there is corrupted code in your update due to vagaries in data connection via your WiFi, then the only thing a Hard Reset via software on the phone or physical button presses - the
only thing this can do - is cycle you into the same problem set.
Have you tried a clean install to the latest official via Lumia Software Recovery Tool?
Are you on Preview for Developers? P4D is non-optimized generic code. One size fits all devices core OS advancements. Various updates can and will and have been reported numerous times to cause issues and glitches with any handset.
I recommend a halt to P4D and a clean install with LSRT. Using the most stable software base available, determine if your phone still has so many issues and if so, seek qualified repair or replacement. Your hardware must be faulty in some aspect or another.
Find the LSRT here:
FAQ - How can I recover/reset/restore my phone software? - Microsoft - USA