Why does FPS drop when switching from Unity 5.3.4 to 5.4.2?

Hi Guys,

My team and I have been working on a project in Unity 5.3.4 for a while now, and we've wanted to upgrade to 5.4.2. The only problem is that there is a noticeable 20-30 fps drop in our scene in 5.4, and we can't figure out why. We ran multiple tests with the profiler, and all of the batches, setpass calls, and memory usage seems about the same on 5.3.4 and 5.4.2. We checked the player settings and quality settings, making sure that everything was setup the same in both projects. I've scanned the forums relentlessly for a similar situation, but none of the details matched up to our situation.

It would be a lot easier to troubleshoot if there was just some kind of indication as to what is causing the drop. The only thing I noticed was that the fps went back up to normal range after disabling shadows in the quality settings. So I wonder if 5.4 has a harder time processing shadows?

But then again, it's expected behavior to have a boost when you disable shadows, so I'm really just grasping at straws here!

All I know is we'd really like to upgrade to 5.4.2, but the framerate drop needs to be addressed before that can happen.

Any help on this would be greatly appreciated!