Very slow tubeless leak won't seal
After more than a year of tubeless bliss -- no issues -- I have encountered a persistent very small leak that simply won't seal. I can ride all day but the tire will have gone down from 60 psi to 40 psi and will need to be topped up. They are fairly large tires (700x40 Schwalbe Almotions) and I am a heavy rider hence the 60 psi.
The tires are tubeless-ready but the rims (Dyads) are not. The rims were prepared using tubeless rim tape and have a tubeless schaeder valve. They need steady pressure for an initial seal but after 5-10 seconds of dribbling they seal up well. I removed the tire and inspected it very carefully for embedded glass or other debris but found none in the three small tread cuts (1/4" max). There was no sign of the cuts on the inside of the tire but I nonetheless put a vulcanizing patch on the inside of the tire at the location of the worst cut and remounted it with new Stan's sealant and a new valve core.
Despite this the tire still seems to lose a bit of air and needs daily topping up. There is no evidence of sealant leakage. Any suggestions?