Questions on 1958 COLOR Raytheon C-21C1-M Television

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Hello, I'm new here so I'll introduce myself. My name is Matthew Clark I'm 19 years old and I've been interested in vintage electronics since I was around 7 years old. The other day there was this Raytheon television on Facebook and I ended up getting it. I hear it's one of two still surviving. With the cabinet I'd like to use Restorer Finish to help hide some of the bad spots. Yesterday I carefully with two screwdrivers took the CRT socket off and tested it. The emissions are fantastic and the cut off is good. When the voltage is reduced to 4.5 volts it still tests good, but there might be an issue. At 6 volts no short, but at 6.3 volts the left shorts light is flashing(Not solid indicating a hard short). The exact same thing happens on a 1968 Zenith color set. With the Zenith I have a decent picture still despite the blinking short light. There's a couple links below of both sets. So my question is, could there be a problem with my tester or is the short so minimal that it will not make the CRT unusable? And can the heater voltage be slightly reduced in the set so it doesn't short if it's actually a short? And should I buy or borrow a known good crt tester. I'm in Kankakee County IL if anyone near me has a good CRT tester they'd let me use let me know. Thanks
LINKS:https://flic.kr/s/aHsmRXbcgr
Video of Zenith playing with possible short. https://www.youtube.com/watch?v=blfC...l=MatthewClark