在智能媒体服务用的4.12.3同样的时间线配置，换了个转场类型就预览失败了，是什么原因呢？

在智能媒体服务用的4.12.3同样的时间线配置，换了个转场类型就预览失败了，是什么原因呢？{
"VideoTracks": [
{
"VideoTrackClips": [
{
"MediaURL": "https://yl-resouce.oss-cn-hangzhou.aliyuncs.com/clipvideo/39fb5e4a6bd344358ca890216abdef8b.mp4",
"Type": "Video",
"In": 0,
"Out": 2,
"Speed": 1,
"TimelineIn": 0,
"TimelineOut": 2,
"X": 0,
"Y": 0,
"Width": 253,
"Height": 450,
"Effects": [
{
"Type": "Crop",
"Height": 1,
"Width": 1,
"X": 0,
"Y": 0
},
{
"Type": "Background",
"SubType": "Color",
"Color": "#000"
}
],
"TrackId": 0,
"Id": 9
},
{
"MediaURL": "https://yl-resouce.oss-cn-hangzhou.aliyuncs.com/2/material/video/17140097849990000.mp4",
"Type": "Video",
"In": 0,
"Out": 6,
"Speed": 1,
"TimelineIn": 2,
"TimelineOut": 8,
"X": 0,
"Y": 0,
"Width": 253,
"Height": 450,
"Effects": [
{
"Type": "Crop",
"Height": 1,
"Width": 0.31690140845070425,
"X": 0.3415492957746479,
"Y": 0
},
{
"Type": "Background",
"SubType": "Color",
"Color": "#000"
},
{
"Type": "Transition",
//"SubType": "swap",
"SubType": "squareswire",
"Duration": 1,
"From": 9
}
],
"TrackId": 0,
"Id": 10
}
],
"Count": 2,
"Type": "Video",
"Visible": true,
"Id": 2
}
],
"AudioTracks": [
{
"AudioTrackClips": [],
"Count": 0,
"Type": "Audio",
"Visible": true,
"Id": 6
}
],
"SubtitleTracks": [

],
"AspectRatio": "9:16",
"FECanvas": {
"Height": 450,
"Width": 253
},
"From": "openAPI",
"LosslessConversion": false,
"SdkVersion": "4.12.3",
"Version": 0
}