Running traffic behavior when SLA is no longer meet at a given Inet link.

On an SD-WAN site with two Inets and SLA configured with Inet1 preferred for a given traffic, when Inet1 stops to meet the SLA what happens with the sessions running at Inet1? From Fortinet documentation I understand that "If at any time, the link in use doesn’t meet the SLA criteria, and the next link in the configuration meets the SLA criteria, the FortiGate changes to that link". Is that just for new sessions? What happens with the existent sessions at Inet1? Those are dropped? Reason behind the question is because sometimes one SLA parameter can be triggered but the link is still usable.

Thanks