The Inspect console is not dedicated to your extension and may accumulate noise from other activity in the browser. I suggest creating a new profile to avoid interference if you can.
Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.
Take a quick glance at the page and make a mental note of which Profile has this notation: This is the profile in use and it cannot be deleted. That is your current default profile.
Click the “Create a New Profile” button, then click Next. Assign a name like ExtDev, ignore the option to relocate the profile folder, and click the Finish button.
Firefox will switch your default profile to the new one, so click the Set as Default Profile button for your regular one to avoid an unwanted surprise at your next startup.
Scroll down to ExtDev and click its Launch profile in new browser button.
Firefox should open a new window that looks like a brand new, uncustomized installation. (Your existing Firefox window(s) should not be affected.) Please ignore any tabs enticing you to connect to a Sync account or to activate extensions found on your system to get a clean test.
You might need to enable some developer preferences, but I can never remember them… (I also bookmark about:debugging for quicker access.)
When you are done testing, you can close the extra window without affecting your regular Firefox profile. (ExtDev will remain available for future sessions.)