SurfaceTexture.getTimestamp () returns 0 during playback

I recently ran into an unusual issue on Android 5.0.2 (API 21). My app uses SurfaceTexture to display video. The playback engine is mostly based on google / grafika CameraCaptureAvtivity, but the video source is decoded by .mp4 movie file instead of camera. The app worked fine until I ran it on a Galaxy S6 running Android 5.0.2 (I previously used 4.4.2 and 4.4.4 devices). The problem is that every time I try to get the timestamp from SurfaceTexture with getTimestamp()

, the method returns 0, although the playback is fine. On other devices that I mentioned before the time stamp was correct.
Can someone tell me if this could be an Android bug? Is there a way to work with it?