Ring Pro (wired) not ringing inside - intermittent

Hi. I have installed the latest version of the doorbell and have noticed sometimes it rings outside but not inside on my chime. When I test it it rings fine. I cannot replicate the issue. Happens intermittently. People have walked away and packages returned to sender because of this. Router is placed behind TV Health Check indicates that everything is good but I should look to upgrade my transformer for future updates. Electrician who installed said the last Ring doorbell was faulty so he replaced that but not the transformer which came with the bell. Could it be the Router placement?