Do you have firewall logging enabled on the Peplink Balance 30?
We have identified some stability issues in firmware 5.4 series, which affect Peplink devices with heavy firewall logging turned on, and may cause inaccessible web UI over a few days of use.
For Peplink devices already running on 5.4.1 to 5.4.4, you are advised to check and turn off all firewall logging options. We will have a new firmware release some time by next week. You may download and try the new firmware once it is officially release.
If that is not the case, you may setup a Remote Syslog server to capture the necessary log for more information. If you need further assistance, please log a ticket to http://www.peplink.com/contact/support/