I have looked and can't find a post with this exact issue.
2015 F3-SM6.....

Parking brake will set 99% of the time, releases on first try maybe 50% of the time, flick the switch back and forth, and for now will eventually release.
Also dash initiator light for said brake does not come on at all.
It was working fine for the past 26,000 miles I used it all the time. Going to dig into tonight but thought I would post up in case someone has an idea.