So long as you still have the original tape, you might be able to try some different captures. My personal copy was recorded on VHS at the four hour EP speed, but I was able to transfer it with a Panasonic AG-1980, and got decent results. Mine is missing a few seconds at the commercial breaks from hitting the pause button back in '84. I didn’t have a lot of tapes at my disposal back then!

I’ll wager your recording has better audio.

I wonder if my Betamax has the same circuitry?

Just out of curiosity, do you have anything else on Beta?