FPS Change

I recorded a gameplay from my Android phone and imported the screen recording to my PC to be edited with DaVinci Resolve. After some editing, when I export it, the FPS change significantly which make the video looks poor. (According to K-Lite Codec Pack, the screen recording FPS is around 52. When I export the edited video, the FPS shows number around 20.) But when I edit a screen recording that is recorded directly in PC, the FPS won't change and the exported video looks like the same as the raw one. How is this even possible? What should I do to get the same quality for the screen recording from Android?