Tekin ESC puts out 6v and 8v. It says 7.4 just as a generic label for HV but the actual output is 8v.
That is actually better than 7.4v for a true HV servo that is intended to take up to 8.4v, but it may not turn out well for a servo intended for 6v.

I have heard of people running those at 6.5 up to 7 volts without issue but it may be a bad day for that savox running it at 8v.

The savox burning up may be the best thing for you though. Those are good cheap servos but they work best in lower amp draw power systems like 2wd buggy, ST, SCT, 4x buggy and 1/8 buggy but a majority of the issues reported with those are in a 4x SCT (especially with a spectrum radio). Its the perfect storm.

I stripped a gear in a airtronics servo a couple years ago that was about a decade old in the 2nd heat. Replaced with the savox which was the only servo the track had for under $175.
Threw it in my 4x SCT running RX8.1 and tenshock 4600.
Got through 2 warm up laps and couldn't line up for the start without running into people, steering was starting to get glitchy and strange... what the heck?! Tone beeps, we're off, couldn't get more than a couple of turns into the first lap because the steering was all over the place. Days done.

Sent the ESC into Tekin and the bec was burnt out. I would assume from the minute it was run with the savox. I had ran it with the airtronics servo for about 6 months without issue. The minute I bolt the savox in, burnt up the bec in a ESC known for an industry leading bec.

That same savox has been in my B44 for over a year without a glitch or any hint of an issue powered by a rs pro. Fantastic servo!!!... in a 1/10 buggy.

Mainly just wanted to point out that the 7.4 setting in the RX8.2 will deliver 8.4, not 7.4v but the story went from there