Why can't remove playview from its parent or call clearSurface in 2.8.1

[imcloud]

ExoPlayer version = 2.8.1

I called this after start play

removeSelf(playerView);

OR

player.clearVideoSurface();

then got this error

E/ACodec: new surface holds onto more buffers (2) than planned for (1)
E/ExoPlayerImplInternal: Internal runtime error.
                         java.lang.IllegalArgumentException
                             at android.media.MediaCodec.native_setSurface(Native Method)
                             at android.media.MediaCodec.setOutputSurface(MediaCodec.java:1810)
                             at com.google.android.exoplayer2.video.MediaCodecVideoRenderer.setOutputSurfaceV23(MediaCodecVideoRenderer.java:915)
                             at com.google.android.exoplayer2.video.MediaCodecVideoRenderer.setSurface(MediaCodecVideoRenderer.java:405)
                             at com.google.android.exoplayer2.video.MediaCodecVideoRenderer.handleMessage(MediaCodecVideoRenderer.java:372)
                             at com.google.android.exoplayer2.ExoPlayerImplInternal.deliverMessage(ExoPlayerImplInternal.java:861)
                             at com.google.android.exoplayer2.ExoPlayerImplInternal.sendMessageToTarget(ExoPlayerImplInternal.java:829)
                             at com.google.android.exoplayer2.ExoPlayerImplInternal.sendMessageInternal(ExoPlayerImplInternal.java:811)
                             at com.google.android.exoplayer2.ExoPlayerImplInternal.handleMessage(ExoPlayerImplInternal.java:328)
                             at android.os.Handler.dispatchMessage(Handler.java:107)
                             at android.os.Looper.loop(Looper.java:207)
                             at android.os.HandlerThread.run(HandlerThread.java:61)

And, first call player.stop() will no error but lost player state

qs1: what is this mean?
qs2: how can I switch surface and keep player state

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UPDATE

caused by configChange, activity call oncreate twice