Captive Portal - Allowed MACs cannot download

[thekeymaker]

Situation
- Installed Latest 17.7.1_2
- Configured everything
- Added MAC addresses allowed through Captive Portal
- Devices which were added cannot download files >30MB or so.. -- it starts but the download gets interrupted

Note: Removing the same device from the MACs allowed, then logging in through the captive portal, allows the same device to download without any problems.

Anyone have any ideas?

Thanks!