All of mine will freeze on "low fan" speed. Not moving enough air to cool the room, so the compressor stays engaged all the time (doesn't have time to thaw). Turn your thermostat down a bit, turn fan on high and it should cycle on and off. These high temps and  high humidities just add to the problem. Check your filters, they are small and it doesn't take much dust and debris to clog them.... I'll dust our's about every 24 hours running, specially if we're showing out of the trailer... Alot of outdoor stuff ends up in that filter very quickly.

I have found that the condensor(sp) gets dirty and causes the water to sit on the fins and once it starts to freeze it just continues doing so until it's completely froze. I have had good luck using aluminum wheel cleaner(has some acid in it) on the condensor. Just remove the cover and spray the cleaner on the aluminum radiator looking part towards the rear, then blow it out with a good air compressor. This should fix your problem.