There is an issue in Xpress applications created in 2.15 that could cause fonts to become unreadable on tools or animations such as making tools hidden based on a bool expression.
To avoid any issues upgrading the 2.15 versions of projects, follow the steps below:
Make a copy of the original application to be used for the upgrade.
Open the copy of the project and it asks whether to upgrade or not, use the drop down menu to select version 2.17 and do the upgrade.
Alternately, highlight the copy of the project in the Local machine tree and use the "Upgrade Project" button which is forth icon from the right, just above the local projects tree.
Select 2.17 as the upgrade
Open the 2.17 project and verify there are no problems with Fonts or animations.
Repeat the process above on the 2.17 project upgrading it to 3.1
Now the project should open and all of the Fonts and animations will be OK.