Why are my tubeless tyres burping?

Following on from the other tubeless burping thread and to avoid hijacking I have been meaning to post my own question.
I just built my new bike and chose mavic 821 rims with hans dampf tubeless ready tyres. I have ridden it about 5 times so far and burped on 4 of the rides and on 2 of the rides burped multiple times.
Every time it has been around a 1 – 2m landing onto off camber ground from a jump or drop. Both front and back have burped.
I wouldn’t normally ask this question as an off camber landing isn’t ideal and will always be more likely to burp but I have been running tubeless hans dampf front (exactly the same model as new bike) and nobby nic rear now for around 3 years on mavic 819’s and never burped once. Same jumps and conditions and some much worse landings I shouldn’t of got away with. Pressure is about the same and I have tried a higher pressure on the new bike but it made no odds.
Everything I read said that the wider 21mm 821 against a 19mm 819 rim would be better for tubeless.
The most annoying part was having to borrow a mates bike to go fetch a pump as I have had no punctures or issues for so long I don’t bother carrying spares or tools when riding locally.

Thanks

Andy

Can’t help with the question on the 821 rims, but my 819 rims have also been perfect for 3+ years. Not a single burp with proper UST Maxxis tyres (so a bit of a weight penalty).

Also worth mentioning that I also run tubeless on crossmax st’s and stans crests whatever they measure and have never had any problems with these either.

What tyres are you running?

Look up ERD and ETRTO

Just checked the rims ETRTO and the 821 is 559 X 21 and the 819 is 559 X 19.
The hans dampf all have ETRTO: 60-559 (26 x 2,35″)

How old are the HDs? we’re they on your old rims before putting on your new rims?

They are new tyres on new rims.
I put them on with a tube in for a few days to shape before taking the tubes out and putting the sealant in. Both went up easily tubeless with a joe blow.

how much pressure?

I normally run around 30psi on the 819’s. I tried that first ride on the 821’s but it felt very hard but burped. I increased to 35psi and it still burped.
Even when I have not bothered topping up the tyres on the 819’s and they have been as low as 15psi they have never burped.