pfSense

This does appear to be a duplicate of #9183, though it doesn't affect LAGG in general as that is working fine on current versions for nearly everyone else. The other issue was primarily focused on an unsupported configuration where LAGG was used with OpenVPN, but that should not affect LAGG configurations on normal interfaces.

This site is not for support or diagnostic discussion, however, so I suggest you post on the Netgate Forum and supply more information about your configuration and environment. There must be some aspect of your setup causing it to not work for you when it works for everyone else.