Not willing to try and 'back out' Android 5.0.1 to 4.4.2 from my Samsung S4, I searched for solution to 5.0.1 issues. This is what I found:
http://www.androidpit.com/galaxy-s4-lollipop-problems-and-how-to-fix-them
I went ahead and cleared the cache and turned off all window animation, transition animation and animator duration scale using the instructions in the link above.
After completing these two changes, I powered up the P3A, controller, S4 and started recording. The changes appear to have fixed the increasing lag issue I had last evening using the same test configuration. I let the test run for 10 minutes and did not noticed any lag longer than ~300mS. I have not flown with these changes yet.