Thanks all,
It seems pretty clear that this is a production control issue at Schwalbe, not a consistent problem. Though I suspect the new tread is more prone to collecting bits in it. Some of our own team members went all the way with only one or two punctures with XR's (compared with more than twenty each for my partner and I). Others acheived the same thing with different brands, as is my own past experience, with both Schwalbe's and others.

Still if I can't rely on them to work every time I'm not going to use them. We risk getting stuck under the sun with temperatures in the 40's down here. (As it was in China and central asia)

Just to be clear, these were the regular marathons, not the plus or the XR. The XR seems to have similar puncture protection system though. The plus has a heavy lump of plastic in it, which increases rolling resistance and weight.

We did not use XR's because of the slow tread pattern, excessive width and low pressure rating. We were riding full suspension recumbents so no need for soft wide tyres. In any case they are not available in 406mm ERD.

The problem went away with tyre liners after I reached Germany, but this is no good for record attempts, solar racing etc, here in Australia.

Cheers

Olly