Classic Rear wiper problems.

For a while now I have been having trouble with the rear wiper on Buttercup - 1988 2.4 VM - removed and cleaned the contacts on the switch, twice, each time seemed to fix the problem of the wiper not working. The last time I did it a couple of months ago, everything seemed ok after. Then today used her and as there was a fair bit of dust on the rear screen tried a wash/wipe, all that happened was a jet of fluid, bugger, looks like new switch time. Couple of miles up the road and all of a sudden the wiper is working??
This makes me think the switch is not the problem, could it be the relay??

I think the RRC uses the same wiper as 90/110s? Even so they are all pretty similar. The one of my 90 didn't work as the shaft had seized in the tube. New ones are silly money. Watched one of Mike's Britannica Restorations video #1187 and took it apart and fixed it. Easy. If the plastic gear has broken you can get them on eBay.
More here: https://www.landyzone.co.uk/land-ro...-90-110-130-today.342736/page-60#post-5145745

I don't know the answer but would like to say I never really worked out how to use the rear wiper on mine.
It always seemed to be a lottery of flicking the switch one way or the other until it eventually stopped. Then sometimes it would start again 30 secs later.
Either way 15 years since I drove it so I'm sure its seized up now

If it's the column mounted stalk switches they can be a PITA.

The front wash/wipe on mine played up - sticking and/or not working.
Took it apart - inside a plastic bag just in case anything wanted to ping off into the distance - & wear of the plastic body was the problem.
Springs & small ball bearings in it which make contacts on strips of brass (which can get dirty) which were contained in the plastic bag as they tried to take flight!
Improved a bit but still not right.
Bit of luck that a used one came up on ebay a couple of weeks ago for around £25 & that solved the issue.

Back one sometimes sticks but not a major issue at the moment although much the same as you it does benefit from being used.