FortiSwitch not Applying Configuration from FortiGate

Hi all, 

I am having issues syncing configuration to my managed FortiSwitch devices. Currently, I am running FortiOS 7.4.4 and FortiSwitchOS 7.4.2 and when issuing a execute switch-controller get-sync-status all I get the below status, MAC and REST API login error. 

FGT01 # execute switch-controller get-sync-status all
Managed-devices in current vdom root:

FortiLink interface : fortilink
SWITCH-ID (SERIAL)                    STATUS CONFIG         MAC-SYNC       HTTP-UPGRADE
Switch-A (SN12345667785654)      Up     Error          Error          -

[1]
 command: https://10.10.10.1:443/api/v2/login
 payload:
 result : REST API login failed with error 60
Switch-B (SN41233434554657)      Up     Error          Error          -

[1]
 command: https://10.10.10.2:443/api/v2/login
 payload:
 result : REST API login failed with error 60

I have another setup in a different location running the same version except the only different is that the tunnel-mode is set to compatible and I have no configuration sync issues: 

config switch-controller system     set tunnel-mode compatible end       

Investigating this it seems as though this is a fix that people have identified and an issue that is apparent in the FortiOS 7.4.4 and 7.4.5 versions. It is also documented that this is still not fixed in FortiOS 7.4.5 and want to know if this is has been resolved in 7.6.0? I will likely be upgrading to this version because the below issue has been resolved:

On the System > Firmware & Registration page, after upgrading the version 7.4.2, the FortiSwitch shows as not registered in the GUI.

Regards, 

Dan.