Tubeless tyre randomly going?

I had a similar issue with a 3mm sidewall hole that would only seal at 30psi, anything higher and it couldn't quite get it.

I used weldtite tubeless repair string on it and it worked great (still fine 6 months on). These strings are quite thick, more MTB based I guess, but work well on 3mm holes. Smaller strings are available too such as the genuine innovations which I found could not seal 3mm holes (and anything smaller the sealant can cover so these didn't work for me), links below:

https://www.evanscycles.com/weldtite-tubeless-patch-kit-00103371?esvt=54...

https://www.tredz.co.uk/.Genuine-Innovations-Tubeless-Tyre-Repair-Kit_36...

If anyone in the Liverpool / Manchester area wants a nearly new Airshot for a bargain price, email me at guyrwood at gmail dot com. I've given up on tubeless.

I had problems with the 'string' repair kits, I just made the holes bigger in *2* tyres

these are much better:

https://www.acycles.co.uk/zefal-tubeless-repair-kit-10369.html

super thick patches, held out so far (I slashed open a brand new G-one speed on a tow path within a week of getting, 6 weeks later is still fine after repair)

if you're using this method, then take the tyre off and give it a nice soapy wash first, get it all nice and clean. The airshot compression chambers are pretty useful too:

https://www.evanscycles.com/airshot-tubeless-tyre-inflation-system-EV285127

it is a bit more a faff all round, but I think it's worth it overall once you get it right

Put a tube inside. Sorted. 

You can patch one of those, a tangible repair, or simply replace it. 

I've watched too many videos of folks faffing around trying to get tubeless seated for the first time. Really. I love fettling - but it's all too much of a fuss.

Still heavily underwhelmed by the whole tubeless-for-road phenomenon. 

I've used the vulcanised 'string' kits for repairing holes and tears that wouldn't seal, and they seem to work well - for example: https://goo.gl/6AdJdU

I had this issue recently too - i think it is worse if there is a foreign body still stuck in the tyre.

Whilst I did take the approach described by CR94Di2 - I'm not sure it really helps. I think it's the action of the air escaping that gets the fibres in the sealant where they need to go.

I repeatedly tried to get air flowing out of the hole by inflating the tyre to maximum pressure. You tend to get the situation you describe - walk off to make a cuppa and psst, out it comes when you least expect it! Spin the wheel and it should seal up. Then reinflate and repeat.

Once it stops giving up dramatically, take the CR94Di2 approach. If it's still seaping you'll get a damp patch on the tyre letting you know it still not fixed properly. If there's no damp spot after a night then everything's rosy. 

I think I'll get a tubeless tyre repair kit and give that a go at some point.

I've got a few holes that keep re-opening.   Having had a good look at the tyre, it's not worn but it is cut to pieces.  Must have had a few unfortunate route choices.  New tyre time - there are a few patches inside it already

Yes, leave the wheel with the puncture at the bottom postion so it sits in the sealant for a good while, to get a good seal.  If it keeps failing then it might be too big a hole for the sealant, eith patch or inner tube.