AF 772 diverts with loss of IAS?
 

Interesting one - AFR 772, shows an IAS of 84 kt for some time, squawks 7700 and then diverts.
Loss of pitot / IAS a-la 447?
https://cimg7.ibsrv.net/gimg/pprune....48f5a25d6d.png

Well, this is a 777, in the day time and with relatively tame weather. Still an interesting one indeed.

Tame at that point, but look at the whole track, they deviated several times around storms after Forteleza, and data shows several periods of incorrect (307 & 84 kt) IAS mid ocean. Those 2 values reoccur just before the divert, looks like an instrumentation fault and fallback values.

Well spotted - definitely something fishy there !

That being said they seem to have passed Porto when they elected to divert so whatever reason they had it seems it actually escalated at that point.

And they are back flying now...

No.

The errant readings are GPS-derived groundspeed, no connection with pitot pressure.

Moreover, they occur during the part of the flight that, according to FR24, is out of ADS-B coverage. So they are made up, not data received from the aircraft.

There doesn't seem to be any evidence that the diversion had anything to do with instrumentation issues.

They don't all occur out of ADS-B coverage.

I stand corrected - it looks like the succession of 307 kts values were while out of coverage (05:02-06:33), and the subsequent 84 kts readings when back within range (07:02-08:40).

The 7700 squawks didn't start until about 10:20, so I still can't see any obvious connection between the emergency and the dodgy ADS-B data.

Reported elsewhere that this was a medical divert

Given the timing (about one hour on ground) and profile flown (they basically turned back to Porto, clearly not an ongoing issue developing in flight) I'd say it is the most likely explanation.

As for the Fr24 bogus data not idea 🤔

In normal times, around 90% of all 7700 squawks are medical emergencies.

I have it on good authority, that it was in fact a medical emergency.
I should know better regarding spurious ADS-B data, its just they were consistent values and over longer periods of time than a few missing points.