iPhone 8
iOS 11.2
2016 Lincoln MKZ with "Sync with MyLincoln Touch" - latest version according to Lincoln's "Vehicle Health Report" diagnostics.
When on a voice phone call, the Bluetooth HFP (hands-free protocol) connection between the iPhone and the car will repeatedly disconnect and reconnect resulting in the other party experiencing about 15 seconds of "dead air" during which they continue to talk while unaware that I cannot hear them. The time interval between episodes appears to be random and unrelated to anything else. Since the use of hands-free is a legal mandate in my state and the use of headphones while driving is a safety issue, I have little choice but to seek a resolution to the problem.
Streaming audio which uses A2DP (advanced audio distribution protocol) works fine.
My LG Tone HBS912 (Bluetooth 4.1) works fine for both calls (HFP) and music (A2DP).
I went to the Genius Bar yesterday and although the techs had "heard of" the problem, they had no definitive fix. I allowed a tech to do a factory reset on the phone through iTunes and then did a master reset on the Sync system in my car. I then paired phone to car and tried again. The call disconnected / reconnected about 3 minutes into the call. About 2 hours of total time wasted in that effort.
My *guess* is that the Bluetooth 5 on the iPhone 8 (and X) is not fully backwards compatible with some Bluetooth 4 devices. Users will perceive this as a phone problem since prior iPhone models worked fine in their car, and rightly so. The auto manufacturers will not likely pursue a fix since they, too, will see this as a problem that Apple created and Apple should fix.
Thus, we wait for a permanent fix from Apple.