Two previously working scripts stopped working when trying to sync on text in the page. Window identification was also no longer working.
Various workarounds for some scripting issues were tested and they found some that worked around the Invalid Window error when trying to use the NimRecorder Spy Tool. Most of the issues had to do with accurate window identification.
We had to use the browser DEV tools (F12) to manually identify windows/elements etc and manually configure the UseWindow/UsePage functions as the customer's webapp is highly customized and doesn't respond with normal default browser behaviour.
Note also that the Nimrecorder sometimes threw a brief blue window reporting an error with the browser extension but its only temporary and as long as it disappears, it can be ignored.