Seems like the Nexus is really kind of sensitive.
Did you try this already:
Although requested once it's not supported on the OnePlus One. Read here why (hope you at least understand some of that )
For Repit it's ok to reduce it to 8MB (=min). Several people already did that (having a bigger system partition already in place) in favor of a bigger data partition for switching to emulated storage. If you want to go for adoptable storage instead and realize the external SD to be slowing down things, the emulated storage would be a way that works.
thanks for your excellent support! sorry that i'm MIA, swamped by work, miss XDA