P: Sometimes deletes all metadata

When editing pictures with lightroom app, I use a lot of selective edits. I save the picture to my camera roll on the iphone. I exit the lightroom program. Next time all of the metadata, or just the latest is deleted. Sometimes I just get the original picture and have to start all over again. I think maybe this is caused by me using more selective edits than is normal. Many pictures can be edited with no problem.