I don't know why MT release only usermanager in this specific version
https://download2.mikrotik.com/routeros ... 6.33.3.zip .
I don't recommend you to downgrade to 6.33
you won't be able to upgrade RouterOS including usermanager package up the V7 release. If you are sure with this condition you can upload the unzipped files and the make /system package downgrade and reboot
Regards