[Phlogiston]

OK. I tested 6 tubes on my Hickok 533 that I calibrated last year. Two were NOS both tested near 2300, neither showed any signs of shorts. Of the 4 used tubes one was like new, no shorts. Two had the #3 position show flickering shortlamp after warm up lasting about 10 - 30 sec. One that tests near new had the #3 position remain flickering until I removed the tube.

Maybe your tubes are used. They will probably still work.