You can't change the icon of a spell more than once in mobile app.

When using mobile app, the spell icon editing in the workshop seems to be busted. When I try to change the icon of any spell for the first time it works fine, but the second time it gives an error saying “An error occured, please try again“. And it never works afterward.

Additionally, there is a similar bug with the dialog popup for the editing screen. Normally when you hold the dialog window that pops up when you start editing something, and you pull it down; it disappears, allowing you to remove the dialog window. This stops working entirely when you change the icon of a spell once. Afterwards, the dialog window never gets removed no matter how much you try to hold and pull it down.