By "teeter-totter", do it feel like the hitch point is moving up and down, from a "V" to an inverted "V" causing the front passengers to bounce in their seats a bit? I call that "porpoising", and it can be sickening.
I believe this is caused by the actual TW of the trailer being too close (or over) the TW rating of the WDH. More specifically, the spring bars are not stiff enough to keep the 2 vehicles "in plane". They need to be flexible enough to not jar your teeth when you go thru a pot-hole, but stiff enough that they resist this type of motion.
What is your loaded weight and loaded TW, and what is the rating of your WDH?
I recommend being at least 100 lbs under your WDH rating.
thebrakeman ('70), DW ('71), DD ('99), DD ('01), DD ('05)
2004 Surveyor SV261T (UltraLite Bunkhouse Hybrid)
2006 Mercury Mountaineer V8 AWD Premier
Equal-i-zer WDH (10k), Prodigy Brake Controller