I have been using Adobe Character Animator since it was in beta. In 2019 I purchased a synology NAS and moved away from Dropbox. I installed Synology Drive on my computer to sync with the NAS. When I was animating characters I would get a Error (2.1.1.x7) Invalid File Tag notice. If you get this error you need to turn off synology drive and and start a new project. and remember every time you use character animator to turn off synology drive.