C1500 SIP PAFL Selection

I‘m using a C1500 Surface. Whenever I have multiple PAFL busses configured (for example when starting on the MultiSurface Template), I cant switch PAFL‘s in the SIP section. I can touch the little field for the PAFL selection, but the touch and turn knob doesn‘t get assigned, so it doesn‘t change PAFL‘s.

C1500&CDM32, V2.12 Rev. 94091

Is it my user error or a bug?