Assuming the One and Port are grouped they’ll be in sync at their own outputs. If the audio from the A9 is out of sync then it must be adding its own internal processing delay. 

The B&O A9 line-in audio-delay is mentioned elsewhere online - one example (of many) I found:

http://archivedforum2.beoworld.org/forums/t/46412.aspx

On some sites there is mention of the B&O App with the various generations of the A9 speaker and that there is an option to switch off the delay, but not sure if that feature may apply to all generations of that speaker, or it’s RCA port(s) so it may depend which A9 version you have?

I got it :-)

inside the B&O app - settings - Line In - you can remove the delay.