Something very strange was happening on my dev sites on SharePoint online.
Suddenly, my app parts “lost” all their custom properties and when ever I would go to add/edit an app part to my pages I would only see the built in app part properties groups: appearance, layout and advanced:
After reporting this to Microsoft, I got the following KB article back as a possible solution:
It suggested a new feature that was introduced a while ago and turned on by default to everyone could be the cause for this issue.
It suggested to allow custom scripts on my site pages, and that should do the trick. Now, there is a note in that settings page saying it might take up to 24 hours for this change to take place after you visit the settings page, so did it work?
I did confirm this issue happens with all app parts that have custom properties, I have tested few other app parts from the store and they all exhibited the same behavior on my dev sites.
I guess I will test it tomorrow and have to update you… fingers crossed…