I've had all kinds of issues with my iPhone 7 Plus, however I think it was probably my own fault:
The Solo3 worked flawlessly with my 6S Plus, but when my 7 Plus finally arrived I just went through the W1 pairing process on it and started using them. After a few hours they would first lose the battery level indication and then lose connection altogether, and I had to restart the iPhone to get pairing to work again.
I tried a bunch of times to forget the Solo3, accepting it would remove from all my devices and re-pairing only to have it happen again.
I *think* the issue was that I was doing this at work, and my 6S Plus and MacBook Pro were both at home (the MacBook lid closed, 6S Plus battery dead), so not getting the "forget the 'phones" instruction through iCloud.
Yesterday I checked all my devices and found the MacBook and 6S Plus both had the Solo3 listed in Bluetooth after I'd told my iPad and 7 Plus to forget them. I forgot them on each device individually, logged my 6S Plus out of iCloud, reset the Solo3, and paired again with my 7 Plus. So far so good since doing that.
Before I switched iPhone they were perfect in terms of connection, the range is awesome, and the battery at least as good as it says, so either my 7 Plus is dodgy (please, no; my 6S Plus was DOA and it took long enough to sort that out here in NZ where the Apple Store is on-line only, without having to deal with Jet Black supply issues), or it was an "echo" of the first pairing in iCloud causing issues on the new pairing.