To give you a bit of insight, around the same timeframe (late October/early November) I directly observed two high-accuracy RTK GPS receivers reporting high accuracy (2cm), full 3D DGPS lock with carrier phase, and positions wandering within about a 5m circle horizontally. The altitude was staying pretty consistent (within about 1m, which was outside of the reported accuracy but not bad) until there was a sudden 60m altitude shift. This was all while they were sitting static on the ground, verified both by the crew and the accelerometer, gyro, and RADAR data.

There wasn’t a software fix per se, but we were able to quickly add a check to verify that the Kalman Filter’s position variance estimate was on the same order of magnitude as the accuracy level that the receivers were reporting and put a big red warning up. This wasn’t a flight-critical system, but it is the first time we’d ever seen that behaviour from those receivers and we’ve used them for 5 years.

Perhaps it's improving the checksum algorithm on network packets, or even ... adding one.

It comes down to voting algorithms and memory persistence. Sometimes there is a threshold before data are "voted out".

I don't work on the A320 but solar radiation is a well-known issue in avionics, generally speaking.

Edit: deleted some speculation

Finally turning on the ECC RAM option?

About one third require hardware mods.

Maybe there's a range that requires a change?

Now imagine, if it was over the air update, then maybe there would be no disruption?

Agreed, I expected additional shielding or something physical like that.

s/solved/mitigated/