You created the forms so I assume you used Acrobat Pro on another system and made a form there. Try bringing in a new copy of the original form and see if it is affected. Also check the app showing the problem is Acrobat Reader and if it is please tell us the exact version.
By the way Acrobat Reader DC does update silently without a reminder. You consented to this when you accepted the license which includes:
7.2 Updating. If your Computer is connected to the Internet, the Software may, without additional notice, check for Updates that are available for automatic download and installation to your Computer and let Adobe know the Software is successfully installed. The Software may automatically download and install updates from time to time from Adobe. These updates may take the form of bug fixes, new features, or new versions. You agree to receive such updates from Adobe as part of your use of the Software.
Sorry one more answer. No this does not sound familiar.