Hey Shrinivas. I was able to recreate the problem in a 4000x2160 timeline, rendering a ProRes Quicktime clip to MP4 h.264 3840 x 2160 UHD setting. I have tested RAW .dng file as well, and the only problem I ever run into is when I use the UHD resolution. It actually airdrops if I do 2560 x 1440. None of the clips that I render out of DR15 show the extension .mp4 on my desktop anymore either which is very strange.
The same UHD clip that doesnt airdrop to my ipad, WILL airdrop after I have ran it through adobe media encoder. There is a problem with the way the UHD files are being wrapped in DR15.
This problem was happening for every single resolution I was doing before. it seems to have gotten fixed for but not for UHD. iOS Airdropis not limited to these resolutions or bitrates because I used to airdrop massive 4K videos to my boss's cellphone, with the exact same settings in Davinci Resolve 15 BETA, and still can when I use adobe media encoder. I even restricted the bitrate in the delivery page to see if that was the problem but it isnt, and was never a problem before either.
Here is a project file and clip of mine you can test.
https://drive.google.com/open?id=1Gm5cs ... 6pc9qRa6hq