Flashing up from 5.0 to 5.1 with CM12 nightlies? I have LG G3 VS985 which runs the nightly CM12 5.0 ROM. I want to upgrade from 5.0 to 5.1, but last time I tried just flashing the new zip certain apps I had on the phone were not compatible, such as Google Services, which caused my phone to soft brick every time I booted up.

Long story short, I'm sick of the bugs on the 5.0 nightly.

I'm wondering how to get the latest nightly without deleting all of my data and apps, if at all possible. I'm using TWRP.

I considered flashing a new GApps version specific to Android 5.1. Would that work?
So, I just went through this. I have the LG G3 D851. Not realizing that it went from CM12.0 to CM12.1. You WILL need to get the latest GAPPS. I did not, and ended up hosing my data causing me to have to wipe and start fresh. 

I am now running CM12.1 with GApps for 5.1 and starting the process of logging back in to everything and recover all of my 2-factor authentication. Hopefully this helps you, so you do not have to go through the same.