It seems the whole export video from Slide is flakey
1 Export to 1080 worked right after I started Lightroom but when I tried to do it again to another file it starts but just sat there. A restart allowed another export. The other resolutions work.
2 If you "X" (cancel) out of a video export (any resolution)that is working and tell it to reexport to the same file it tells you the file already exists but if you hit replace it starts but just sits there.,
3 If you "X" (cancel) out of a video export (any resolution) that is just sitting and tell it to reexport to the same file it tells you the "Destination is in Use"
4 Once you have an export that starts and sits, any other export after that even if you use a new name will do the same. (any resolution)
5 If you export a video (any resolution)and it works and then try to rexport to the same named video Lr correctly asks you if you want to replace the file. The file is not replaced.