Thanks for this! I didn't see the update come through, but will see if I can work around it as you suggest. Being a global issue, as you say, def an OS problem :'(
Both my sister and I have the S5 and have this exact same issue starting from Friday night (4th December, New Zealand time). My sister is a quadriplegic and so is reliant upon the car mode for making calls etc - we need a fix!!