Samba server does not show all folder/files unless few are deleted

Question

1. I have Samba 4.14.5 installed on RHEL8.
2. If I create a few subfolders and then create say 500 files/folders there , about 350 show up. But all can be accessed if I give the complete adress in the windows explorer.
3. If I create 350, then all show up. If I create the 351st folder, then one gets ramdomly invisible but it can be accessed if I give the complete address in the windows explorer.
4. If I delete the 351st dir, then the other 350 show up correctly.
5. If I create another subfolder, maybe 200 will show up, so this is ramdom.

The servers is an EC2 instance and the mount is an EFS.

Config in samba.conf

[global]
        realm = SAMPLE.ORG
        workgroup = EXAM
        security = ads
        kerberos method = secrets and keytab
        template homedir = /home/%U
        idmap config * : backend = tdb
        idmap config * : range = 10000-199999
        idmap config EXAM : backend = sss
        idmap config EXAM : range = 200000-2147483647
        load printers = no
        machine password timeout = 0
        log level = 4
[data-robo]
        comment = AWS EFS share drive
        browseable = Yes
        read only = No
        write list = @group1,@group2
        public = No
        path = /data/robo2
        valid users = @group1,@group2
        force directory mode = 777

Thanks,