450AP GPS Sync => 430AP Timing Port

We are trying to connect an 450AP with On-board GPS as Sync Pulse Source, and then propagate it to a 430AP with the rj-11 port.

But, only get the Sync Pulse on the 430AP, if the 450AP is Generating Sync. If "AutoSync + Free Run" selected, and Receiving Sync from On-board GPS, 430AP doesn't get the Sync Pulse.

On 450AP enabled "Sync Output to Aux Port".

It's possible? Any idea how to get it working?