I noticed the last few times my handles didn't respond to my hand were the times my keyfob was out of range.
I have long arms and I tend to do a weird leaning thing while standing far enough away for the door to swing wide open.
I found the range is about my arms length standing straight up. So when I do this leaning thing where I'm a step away from straight up and the keyfob is in the opposite pocket of the reaching hand it won't respond.
However when I rotate and end up using my other hand which pivots the key closer it does.
A bit annoying but it's something to get used to
1965 Mustang Coupe 289 4spd
2003 Land Rover Discovery II SE
2013 Lincoln MKZ Hybrid