I am surprised that it just started to happen with this version on Sailfish X: it's a long standing issue on my Jolla C since more than three or four updates. I would say it mostly happens with old Bluetooth devices, like cars. It's hard to reproduce. Sometimes it works and will work flawlessly multiple times in a row, sometimes it just stops working, and in that case unpairing and pairing again is what worked the best for me (but not always necessary, and not always working).