I've had this issue for a few months now and it's sporadic, sometimes is several times a day and sometimes it's once a week. When a call comes while in the car and I try answer using the HFL it won't let me answer the call. I've tried using the button on the steering wheel and also on the display screen but happens with both. Then when I try to call the person back I can't use the HFL (its like the display screen freezes up) I have to use my phone instead. What could this be?

I've tried un-pairing and repairing the phone but it still does it. I have a 2016 Acura MDX. I have an iPhone 6 in case that matters. Thanks!!

Car is not letting me pick up call using all possible option. After effects is that Phone incoming display stays on screen even call is over. This message will go off only if you keep car off for significant amount of time. Just ON/Off does not help to remove that incoming message. Audio does not work due to call in action, other call also can’t push that message or error away.

So when mine worked it worked perfectly. Then one day it was having trouble similar to what your describing. I ignored it for about a few months and then the module fried itself and started causing parasitic drain on the car battery.
I would suggest taking the knife and cut it out like a bad appendix. Replacing the unit at the dealer is a couple hundred dollars.