Getting only Heart beat and Timesync (111), instead of Srx data

Hi,

I am trying to get Mavlink Data using the SR4. I have setup Serial 4 as Mavlink 1 at 115200 baud, and I am getting a good valid stream of data (reading using a Pi Pico), but it includes only Heartbeat at 1 Hz, and every ten seconds, I get a 111 Message (Timesync?). Through Mission Planner I set S4, with several message groups set to 1 or 4 Hz, then rebooted the AP, but in the Serial 4 I still only get the Heart beat and timesync messages.

Not sure why.