In commit [c509ff8](https://github.com/blindsidenetworks/moodle-mod_bigbluebuttonbn/commit/c509ff827214621de6bfb850f62bbd336ed1a56a) you have added a new "bigbluebutton" font and used
`[class^="icon-"]:before, [class*=" icon-"]:before` (styles.css#L16(https://github.com/blindsidenetworks/moodle-mod_bigbluebuttonbn/blob/41e2e7abc4a2c29b281be6f984608db0fc7c1919/styles.css#L16)) as selector to apply it.
But some themes use "icon-" syntax to display icons too.
For example [theme_moove](https://moodle.org/plugins/theme_moove) use `icon-bell` for notifications and `icon-envelope` for messages.
As your selectors target classes starting (`^=`) or containing (`*=`) "icon-" browser try to apply your font on `icon-bell` and `icon-envelope` which does not exist in it and so appear as broken.