I wanted to post this report for other MFI hearing aid users.
I have Costco KS8 hearing aids and previously a first generation iPHONE SE.
I had intermittent problems with the setup. Both the phone and the aids worked great, but not always together. The aids cut in and out. The phone would switch between the speaker and the aids. If I was streaming meadia or on a call it was especially unreliable. But, if I was doing something strictly local, they worked together fine.
I asked other blind people but nobody reported having this issue; I was sure something was broken on my end. I talked to Costco but they don't know what Vo is, so they were no help.
In desperation, I wrote to Scott Davert at the Helen Keller national center and he suggested that bluetooth and wi-fi possibly cellular connectivity shared the same chip and it could not keep up with the processing demands, especially since I was using VO.
My phone was stolen and I bought a new SE the 2020 generation. All these problems disappeared.
Last Sunday I was at an Amtrak station with very screeching-loud freight trains passing through about fifteen feet away. I was sitting in a plexiglass shelter which amplified their sound to deafening. Even so, I could clearly hear VO reading me the Uber app and I could clearly hear the Uber driver through the KS8 aids when he called me. With the loud trains I could hear absolutely nothing else but the connection between the phone and the aids was rock solid.
So if you have an older iDEVICE that doesn't seem to work well with your aids, it might just be the effect of its slower processor. We use extra processor cycles with VO, and on top of that connecting to the internet and bluetooth, (MFI is just a form of bluetooth) seems to tax the earlier generations of iDEVICES!