Not to get to complicated, but sounds like you might have "Half Wave DC" if they are pulsing at 30 times a second that's what's happening, you are only getting one/half the ac sine wave, it's DC, but it sux for your LEDs.
I don't know anything about the ELIX12, but I have seen a lot problems with the Chinese made WFCO's. Scamp
used to use them (ours smoked) and has since gone to the PD-4045 I recommend below.
For just a few $$ more you can get a Progressive Dynamics PD-4045 that will take care of everything, give you a new AC distribution system, a 45 amp converter (super clean) with 12 fused circuits for anything you might want in the future, and a 3 stage smart battery charger. Usually available on-line for less than $175/ I have installed a number of them in RV's without any problems.