Why does the P1 DIO11/PWM1 output go to zero briefly when AD1 or AD3 are enabled?

I have the three XBee Series 2C modules configured as DigiMesh 2.4 TH. One is a coordinator, (Indirect Msg Coordinator[1] , API Mode Without Escapes. The other 2 are Standard Routers[0] and Transparent Mode[0]. All have DH set to 0000 and DL set to FFFF. I’m using an Arduino type device to communicate with the coordinator over the rx/tx lines.

I have found that if AD1 or AD3 is enabled, the PWM1 output for P1 DIO11/PWM1 goes briefly to zero when writing the PWM value to either the local or remote devices. I have tried preventing this by first enabling AD1 and AD3, getting the values using the IS command (Force sample) and then setting AD1 and AD3 to Disabled[0], but the PWM1 output still goes briefly to zero when setting the AD1 and/or AD3 input to A/D.

I am trying to set the duty cycle of the PWM1 output and at the same time read 2 A/D values. I would like the PWM duty cycle to remain constant while reading the A/D values or updating the PWM value.

Any ideas?

So I think the real question is, why are you not just using API mode on the ADC receiving module and paying attention to that data and not a PWM pin?