It was working perfectly before, but for some reason it's now producing traces like this: https://spark.lucko.me/toSbUqopHi

That profile run was for 300 seconds. And in case it was a permissions issue or something odd, here's one I ran from the console: https://spark.lucko.me/U7IN6jRKE6

As you can see, they have the system information and TPS report just fine, but no capture. And there were no errors in the console or output.

I'm also slightly worried by that max mspt value, but that's something different I hope.

Any ideas?

It might be discarding the server thread - specifying --thread * gives this: https://spark.lucko.me/s1oau5Myev

Apparently specifying --thread Server thread also works to give the expected output. So something to remember for now.