Hello. I just read this. My Lionel UP DD35 runs great. I have no problems. However, my layout has broad curves. Nothing less than 072. My turnouts are all ROSS. Either REG, #4, 072 or 088.
I am thinking your smaller radius switches are the culprit. The Lionel web site states minimum curve is 042. But those Big, 4 axle trucks do not have a lot play in them.
I hope Lionel can solve your problem. It is a shame when we have these issues with brand new locomotives.
Where did you purchase? They may be able to help, either with a replacement or getting the RA number from Lionel.
Donald