It already happened again but I do not remember which version and may be that aleina dragged it from another version, if not reinstall the Transitions and install V.11.0.6
For me if it worked fine v.11.0.6, install v11.0.7 and the transitions created by me and others stopped working, in the new version comes out the message of video not found, I went to the folder C:\Usersantb Document Documents, I went to the folder of the transitions and all the videos have disappeared.
It may be that creating new transitions have no problem ,but with the old ones the videos disappear , I have looked at 7 or 8 transitions and all videos have disappeared and only one .effsrc file remains.
Sorry for my english ,it is translated.