I’m just guessing that if you paired the OPN S1 first to the hearing box, maybe that’s when the TV Adapter “takes” the setting for the TV Adapter box from the hearing aids as was set by Genie 2, which at that time was on the louder volume setting. Then you discovered that it was too loud, asked your audi to change it to a lower volume setting, which the audi did, but then you didn’t re-pair the hearing aids (now with the new change) to the TV Adapter again, so the new Genie 2 setting made to the hearing aids didn’t make it to the TV Adapter, and maybe that’s why it didn’t stick.
This is just a guess, but if that’s what you observed, it may help to perform a system reset on the TV Adapter box then re-pair the hearing aids to it, just to clear any old settings out first to allow the new pairing to take in the new setting. At least if that still didn’t help, at least then you know the hypothesis above isn’t true.
At any rate, it doesn’t hurt to perform a system reset on the TV Adapter box and the only cost of doing that is the extra time it’d take you to have to pair your hearing aids to it again. But at least you know that you start out fresh with nothing old still lingering in the box.
The TV Adapter box allows an unlimited number of hearing aids to be paired with it, but if its firmware is not robust enough, things may get mucked up. If you’re the only one using it, it wouldn’t hurt to perform a system reset before doing a pairing of your new hearing aids to it.