For a few years now we have been having issues with several remote devices intermittently becoming very deaf in that when faulting you need to hold the remote very close to the device for it to work. Other times everything works normally.
The devices in question are the roller door remote and the remotes for both our cars.
Nearby neighbours are reporting the same issues at times.
The penny finally dropped one day when I observed that the fault only occurs during full sunlight so most likely a solar inverter to blame.
If the sun goes behind a cloud or it is night time everything works normally.
I've mentioned this casually to the neighbours who are also experiencing the problem who also have solar panels in the hope that they might briefly switch off their inverter to see if it's theirs causing the problem (we don't have solar).
So far no one has obliged and I don't want to ruffle feathers with neighbours trying to force the issue.
Has anyone else experienced this issue.
I suspect the inverter in question is probably made you know where and has never been tested to see if it meets RFI standards in Aus.
Like so much of the cheap electronic junk brought into Aus via Ebay.

When it comes to spewing RFI around, after "grow lights" solar panel systems are possibly the worst culprits.

Your observations about time of day squarely point the finger at them, IMO.

Illegal radio transmitters are supposed to be prohibited but, even in the USA, where the FCC is much more active than asleep-at-the-wheel ACMA, it is a big problem. Here's just one article on it:

https://www.solar-electric.com/learning-center/reducing-electromagnetic-interference-pv-systems.html/

Switch mode is indeed the greatest RFI polluter other than the RF that rides on the mains. The wireless NBN has to be shut off to calibrate a radio. The 22 year old computer adds its song a 4ft flouro with totally yet another pathetic & unreliable electronic ballast of which all have failed in the new house, or are about to. Generate RFI. CFL's are a menace.

Just wait until you pull up alongside an electric car, truck or bus and you are listening to an AM radio station. You will then know all about RFI. Absolutely no standards are being followed by any manufacturer when it comes to shielding RFI from listeners, it seems.

Its a sad sad overpopulated sick world we live in. Even auntie has realised this by incessantly telling us on their news, that Victoria has a Mental Health Minister. Surely we would be much better of with a sane one?

Under the criminal fraud & deception of privatisation, which is a vassal for the few to make a fortune ACMA, Telstra being prime examples. Then Government funded Old peoples homes (per Royal Commission) have like other privatised units, like the above; just become money making units providing revenue not service. The latter being the most disgusting where you put Granny in there & have her beaten to death, staved to death, but ultimately "bumped off". Having seen this, its been going on for decades, without being seen, up until now.