Hi @geoffs_crystal,
Welcome to the TeamViewer Community!
May I ask you to check your TeamViewer settings on Incoming LAN connections and ensure it is Deny for receiving remote connection for both devices please.
If it is not related to your situation, please share more information about your TeamViewer version and LAN settings. We will be happy to take a closer look.
Hope to hear from you!
Best,
Ying_Q