Ahhh!!!....that particular failure is familiar. Your rim tape and/or valve hole are the issue. The latex tubes are SO flexible that they will find "escape routes".
Disassemble tyre and tube from the rim and remove your rim tape. Very carefully inspect around the valve hole. Any bumps or burrs must be fully removed (file usually.....it's cause by threaded valves rubbing a lip of aul up usually but I had an AC rim that was corrosion damaged). Install a rim tape that sits well or if you have Veloplugs fitted and have corrosion damage (as I did) then I re-profiled it using 2-pack epoxy and sandpaper. All surfaces must be smooth and the hole around the valve must be "tight fitting". If the hole is lose, glue a section of heavier rim tape (I used continental tape on a friend's wheel) over and re-set the hole using a heated item (tip of a soldering iron, in the latter example's case).
Fitting error possibility:
A failure near the valve can also mean the valve was not fully seated. This will cause an "embolism" type failure (internal swelling and a very sudden deflation when the "balloon " pops....typically a subdued pop followed by a near instant deflation).
The error here is that the valve has not been fully seated and has sat up with a gap underneath......the tube flexes and expands into the gap....and "whoosh" she's flat as a pancake in under 2 seconds (more like less than 1 second!). This is often the type of failure if it failed within 5 mins of you setting it to full pressure for the first time.
Fix for this:
Install your tube normally but after you have depressed the valve inward to check none is pinched under the bead, once you have about 5-10PSI in the tyre pull the valve down to seat it fully. This will completely prevent that type of failure.
Those Challenge Latex tubes are awesome!
BTW.....you can fix them with normal puncture repair stuff but don't use glueless patches (they are emergency only fixes, really) and use a small and light gauge patch.
You are gonna love the veloflexes but they really do go down if you even look at a piece of glass from a 10m distance
They are my favourite tyre BY MILES.