The router has been working fine for years, but recently - the last couple of months or so - the wifi has become rather flaky.

Symptoms are failure of devices to connect, or sessions become of poor quality - Zoom meetings degrade to unusability, it takes seconds for keystrokes to be reflected in terminal windows, etc.

And when this happens normal good wifi behaviour can be restored instantly every time by power cycling the router.

When the problems started, the router only had to be power cycled once every couple of weeks. But it's become more and more frequent, now perhaps twice a day.

Any ideas?

One simple thing to try first, is a replacement power supply.

You could backup the router config, reset it to Factory Defaults, update to the latest firmware and then restore the config backup. Unless you have made some recent configuration changes, I wouldn't really expect this to fix the problem - but you never know!

Twenty years of Draytek ownership, tells me that they are generally reliable hardware-wise - only my Vigor 2820 actually died on me - the rest were rendered obsolete by Virgin Media's ever increasing broadband speeds, that they couldn't cope with . (I almost forgot about the 2900g, but that was struck by lightning )

That said, components do degrade with time (notably capacitors), so it could just be old age catching up with it. (The 2832n is still a current product, I think - so I don't know how old yours is).

I can't find any 'teardown' images for the 2832n, but here is one for the older 2860n: https://fccid.io/VGYV2860AC/Internal-Photos/Internal-Photos-2610403 . You could have a poke around in the 2832n and make sure all the aerial wires are still firmly connected etc. It may still have the pluggable Wifi module that can be replaced, or at least, reseated.

I just came across an online ad. for a firm in Hertfordshire that claim to repair Drayteks. (I know nothing about them). https://multimessage.co.uk/services/draytek

What you're describing sounds like wireless retransmissions. Maybe it's something as simple as the wireless channel is on auto, that channel gets too noisy to use and resetting picks a different/better auto channel?

Personally I'd use channels 3 or 4, then 8 or 9. Those are spaced out far enough from other channels to get a usable connection in environments where channels 1-6-11 are overcrowded and give poor connection quality.