@darylprice sending M997 from DWC should be sufficient to update the 6HC to the same firmware version as DSF. I think DSF will only auto update minor versions (ie 3.5.3 to 3.5.4) but not major versions (ie 3.4 to 3.5), but M997 should fix that. See https://docs.duet3d.com/User_manual/Reference/Gcodes#m997-perform-in-application-firmware-update
Ian