Remnant Weak Points

So against exiles and Kett, weak spots are pretty obvious, but I'm very confused about the Remnant.  I get turrets on destroyer, and then red glowy orb in it's chest when it opens.  Nullifiers the big red spot on the bottom.  But observers and assemblers have me confused.  Observers I hit and sometimes it does obvious weak spot massive damage, and sometimes it does regular damage.  Usually I just aim for the center about where the laser shoots from.  I don't know if it's lag or my own inconsistency, but is that the weak point, or is it something else?  I seem to get massive damage when I'm just off of center?  And assemblers confuse me too.  I've heard both glowy crotch area below the light spot, and I've heard the light spot.  Once again, hitting either seems to sometimes result in weak point damage, and sometimes not.  I assume part of this has to do with the general reports of lag I've heard, but I just want to clarify what the weak points are, most specifically on assemblers and observers.