Screeching Squealing 6JS6C Tube

[Arcanine]

I went ahead and located a good, supposedly NOS 6JS6C tube for my Zenith Color. It's an RCA Brand.

The tube looks brand new, and it acts brand new except it makes audible noise that go away with in the first couple minutes of use. Screeching, and some squealing.

Is it gassy? Or is it shorting out? It only starts to act weird when the high voltage kicks in, and then it passes and stays silent as it should. Even when it fusses and makes noise, it's working correctly and the TV has no negative reaction to it.

Did I get a dud?