Hi @Kristi Wildman ,
I'm glad to hear you solve the problem, And thank you so much for sharing the answer so that it can help more people who have the same problem as you.
I would make a brief summary of this thread:
Issue Symptom:
Since Windows 11 upgrade, receiving Cannot read properties of undefined (reading 'map') on SPFx custom app
Current status:
The issue has been solved. The solution is: Update SPFx application. Add an if condition to bypass the properties pane if it is empty.
You could click the "Accept Answer" button for this summary to close this thread, and this can make it easier for other community member's to see the useful information when reading this thread. Thanks for your understanding!