Bulb out warning with no bulbs out

[Pondy]

I have a small issue which is annoying me.
About two out of three times I drive the car the yellow 'bulb' symbol shows on the centre display then goes away and leaves an exclamation mark for a while, then that goes too.
The manual says it's an external bulb gone. Every time it comes up I check every bulb; they are all working and have been continuously. I checked the connector plugs on all of them and they are fully seated. There is no intermittent lamp problems, so don't think it's a bad connection.
Any ideas, cos it's starting to seriously get on my buns?

 

[B21]

If the Alpina has similar logic to similar age BMWs, the FRM module that manages the lights does both cold and hot checks in bulbs..

Cold check is a small pulse of energy not enough to light the bulb to check the integrity of the circuit..maybe that a bulb is on its way out but not yet bad enough to not light up..