Error code 400 occurred, but AD view is not removed automatically

[songhailiang]

Hi,
I'm using GoogleAds-IMA-iOS-SDK 3.9.2 with CocoaPods to play a pre-roll video ad.
Sometimes, when it failed to play a video ad, the SDK report an error with code 400, but it did not remove the AD view.
I got the error message in this delegate:

func adsManager(_ adsManager: IMAAdsManager!, didReceive event: IMAAdEvent!)

the event.type is IMAAdEventType.LOG,
the event.adData is as below:

["logData": {
    errorCode = 400;
    errorMessage = "There was an error playing the video ad.";
    type = adPlayError;
}, "adData": {
}

When this error happened, it will not call the didReceiveAdError delegate:

func adsManager(_ adsManager: IMAAdsManager!, didReceive error: IMAAdError!)

I think this might be a bug of the SDK, when playing a video ad failed, it should tell the app the error and let the app to continue to play the video.

Could someone help to confirm this?
BTW, i'm using Swift

Thanks