R7000P very slow to serve internet, timeouts with just one real user -- solved?

Ho boy, are you going to love this...

Discovered that there is some sort of weird interaction between iTunes and Firefox, when running at the same time doing almost nothing.  Some sequence of packets on certain web pages evidently confounds the router and makes it lose track of reality.  I have no specific evidence, but suspect this is the result of tracking code and scripts buried in places like Youtube, Facebook, and elsewhere.

Running iTunes 12.12.7.1 and Firefox 110 64 bit on Windows 10 pro.  Symptoms are basically the same with WMM, Bearmforming, airtime fairness, or MU-MIMO enabled or disabled

If I have iTunes and Firefox doing nothing-burger activities (playing songs hosted on Netgear's Readyshare disk, sitting on Google's home page), everything runs fine for hours.  But the moment I start using the browser for anything more interesting, I'll have maybe 10 minutes before the network dies.  Once it's sickly, if I kill the browser, the router comes back to life all by itself after a minute or so.  100% repeatable, even with all of Facebook's plugins disabled.

If I do the same browsing routine with the Edge browser, I can go for hours with no problem.

So I'm pointing the finger at Firefox.