Traditionally, I've considered Android operating system point upgrades to be something of a minefield. The jump from Android 4.1 Jelly Bean to 4.2 Jelly Bean, or 4.3 Jelly Bean to 4.4 KitKat, gave me mixed feelings. On the one hand, I would be sure to see some improvements in the device and some old bugs would be squashed, but you never know what might be updated over and above the changelist. With upgrades that sound more major, such as from Android 2.3 Gingerbread to 4.0 Ice Cream Sandwich or 4.4 Kit Kat to 5.0 Lollipop, might appear to give the potential to introduce even more bugs and issues. The difference in the numbers is more psychological but it's true that with an Android system update, there are risks of shall we say complications. This is most obvious in the Nexus camps, where at times it feels that Google uses Nexus customers as an extended beta test, before manufacturers upgrade their own devices. This may have changed with the rush to upgrade devices to Android Lollipop, we will have to wait and see. And it's true that of the three household devices now upgraded to Lollipop from KitKat, there have been very few issues. But what if you do have issues? There are three things to try to see if these will resolve the issues.
The first revolves around the third party applications installed on your device. Developers have had since July 2014 to modify their application and make it compatible with Android Lollipop. Most did but some didn't, and for those applications that don't work over Android 5.0 Lollipop, in an ideal world they won't install from the Google Play Store. If you've upgraded from a previous version of Android, these will have followed, so running them can cause unpredictable results. Sometimes they'll crash or hang, or the display is distorted. The worst case is that they'll interfere with the device and other applications. You may need to try a little investigation: firstly, hit up Google and search for your device, Lollipop, the app name and problems. This may bring up plenty of issues: perhaps it's well known that this application doesn't yet play nicely with Android Lollipop. If this is the case, I'd recommend contacting the developers and providing as much detail as you can. And then you may want to uninstall the application, but keep tabs on it in the Play Store so that if it's updated, you can try again.
The next thing to try - and you may wish to do this after you've removed a misbehaving application or updated your device - is clean the cache partition. This is an area of your device reserved for keeping temporary application data that the device frequently needs. It's designed to save battery by not forcing the handset to re-download the data every time you need it. Unfortunately, old data from former versions of the operating system and applications can not be compatible with the newer version of the operating system and this can cause issues, even after you've removed the offending application from the device. Whilst it is possible to clean the cache of each individual device, there's an easier way using the Android recovery screen. The exact way of doing this varies device by device but on a Nexus, from power off, you turn on the device by holding the volume down and power key until you see the bootloader screen. From here, use the volume down key to find "Recovery" and tap the power button to enter Recovery Mode (this looks like Andy the bug droid lying on his back). In here, you'll see an Erase Cache option; select it with the power key and wait for the device to clean the cache for you. This won't permanently erase any data on your device; once it's done, reboot and test.
The other option is a factory reset. Before you do this, ensure that you have backed up everything on your device - both in internal memory and your MicroSD card, because you'll want to remove everything and re-install applications from scratch. And just to reiterate, I mean everything: you should reformat your MicroSD card just in case. There'd be no sense in partially wiping the device just to discover that a piece of incompatible data on your MicroSD card can be causing a problem. Once you've backed up, go ahead and factory reset your handset and then set it up again. If you've already tried this, you might want to only add the absolute bare minimum applications onto the device that you need. And you may even want to check online with other users to see if they've encountered problems with applications you're considering too.
Nobody likes hunting for fixes on our devices or removing applications that we've come to love, but sometimes these are the only ways to get our devices running smoothly following an upgrade to the operating system. If you've encountered issues with your device, let us know in the comments below - and let us know if you've tried anything in this guide and how you get on.