SSL_VPN - scheduler problem

Hi, I have problem with scheduler for SSL_VPN policy, configured for limit user logons after working hours (only RDP proxy mode, without ssl tunnel mode). Unfortunately random users has problems with login in working hours - permission denied warning. Time and timezone on fortigate is correct. FortiOS version: 6.2.3

I have many fortigate's with older versions of software and the same configuration (scheduler, rdp proxy) and I don't have similiar problems.

Best regards