Upgraded a 60F from 6.4.3 to 6.4.4. So far no issues found.
When we upgraded to 6.4.3 we had the wireless issue and had to wtp-profile, edit "FortiAP-profile-name", set dtls-policy dtls-enabled to get traffic to pass. This hurt wireless speed but allowed it to pass traffic.
After upgrading to 6.4.4 we ran config wireless-controller wtp-profile, edit "FortiAP-profile-name", unset dtls-policy