You may be experiencing an issue where you believe you configured the Access Group correctly, but the users still have full access on all doors.
In that case check all the items below.
Check that the default group setting is No Access if you're using a device to a door.
This means that user will not have access even if user credential is in the device unless the proper access group is configured.
Check that the device is using server mode and time sync with server is on.
A wrong time of the device may cause issues with user access if you're using a set time in your timezone configuration for your access group and the device time is out of sync with the server.
Check that the time is configured properly on the days of the week.
Check that the setting has been properly applied to the doors.
Check that the user has been properly added to the group.
Check that the user is NOT in the Full Access group.
Transfer the Access Group to the device and check that the information in the device is the same as the server by checking Manage Access Group in Device. Repeat for Timezone.
Double check that the user has the access group configured.
Transfer the user to the device and overwrite existing settings.