I'm having some trouble using the join by location feature in QGIS (2.18). I have a data set of ~7000 points, and another polygon data set. Both are ESPG3573 shapefiles. However, when I join by location many points that are within the polygon don't join properly. I get a lot of "NULL" fields. When I adjust the precision, it reduces the number of NULL joins, but also joins some locations inaccurately.
I've tried every geometric predicate and precision adjustment I could imagine.