Yes, if you have several network interfaces, I suspect that is the reason. The code that handles it is here: /opt/kaltura/app/alpha/apps/kaltura/lib/request/kIpAddressUtils.php I suggest you add some debug prints to it to confirm.
As for default_delivery_type, see some details here:
However, since player version 2.48, the default playback method is always HLS, using the HLS.JS lib, unless, the video is shorter than short_entries_max_duration as set in /opt/kaltura/app/configurations/base.ini [300 seconds by default], in which case, the playback method will be progressive [HTTP] since for short videos, using adaptive bitrate algorithms provides no added value.
If you do not wish HLS to be the default, that can be disabled by setting disableHLSOnJs = true in the player's config [UI conf] under KMC->Studio under the UI vars section.