yep.
you were getting dabs in thailand ? were they dark or light colored ?
i found a batch of diamonds that melted different than another batch and different than some shatter. all should have the same melting point as they were all thc. i can only conclude that the one batch of diamonds was cut with cbd flower at extraction time. maybe only 10 percent or so but enough to change the melting point. cbd melting point is higher than thc.
the flower from your other dabs might of had a higher level of natural cbd in the bud. so the melting point difference would most likely come from that.