I have Start 11, and use it to look like Windows 10. I spent a lot of time organizing my pinned icons into folders and making them all Small, just the way I like it. 

All was fine for several days, then one day many of my apps appeared to be pinned again. Easy to spot, because they are all Medium icons.

I wasn't able to select multiple of these to delete them, and struggled through deleting them one by one.

All seemed ok for a while, but yesterday I noticed them pinned again. Except now there is two extra copy of each.

This is very frustrating, especially because I don't know what is causing it. I hesitate to uninstall/reinstall, because then I am losing all my customizations. (at least I think I am, not sure if there is a full backup that can be restored.).

Is this happening to anyone else, and is there a fix?