Menion, you added the option for default POI icons. Should this maybe affect waypoints which are embedded in GPX? Locus picks a black dot as an icon... This is the waypoint format in my imported gpxes:
<wpt lat="51.00066" lon="7.00079"><ele>39</ele><time>2020-04-13T06:09:05Z</time><name><![CDATA[Stop: City]]></name><desc><![CDATA[2020-04-13 08:09:28 MESZ]]></desc></wpt>