Occasional AVPlayer playback error, the AVPlayerItem is available after testing。 Sometimes it can be solved by restarting。

when I played a local video(I downloaded it to the sandbox)，KVO the AVPlayerItem status is AVPlayerItemStatusFailed and error is Error Domain=AVFoundationErrorDomain Code=-11800 "这项操作无法完成" UserInfo={NSLocalizedFailureReason=发生未知错误（24）, NSLocalizedDescription=这项操作无法完成, NSUnderlyingError=0x3004137e0 {Error Domain=NSPOSIXErrorDomain Code=24 "Too many open files"}} why?