I'm unable to set the TA (Traffic Announcement) volume in my Yaris. I've RTFM that tells me to set it when it's receiving a TA. If I do that, the volume changes while I'm moving the volume control (either on the unit or the steering wheel controls), but it reverts to whatever volume the unit's set at as soon as I stop changing the volume.

This can be very annoying as the input level from the USB socket seems very low. I have to wind it up to have an acceptable level and then if a TA comes in, it's deafening.

I've set the 'automatic sound levelizer' to off without any change of symptoms.

I've spoken to my local dealer, but they seem clueless. How on earth can I demonstrate the problem unless one of the staff are prepared to hang around for a TA to occur? If I give it to them I can see it going backwards and forward for ages.

Any suggestions please?