ICOM IC-7100 residual AM when in FM TX mode

[RFDUK]

Are there any IC-7100 users on the forum?
Just got one of these and really love it but found a surprising 'feature'.

When in FM (FIL1) mode, 15 kHz BW for 25 kHz channels, there is loads of AM on the output, particularly at lower power settings, say 20 to 30% of max.

This can be seen on an external power meter. At lower power settings the carrier power reduces by up to 50% on a whistle!

Seems worse on 4 and 6m, but still present on 2m and 70cm.

Do they all do this or do I have a faulty unit I wonder.
Many thanks.