I'm with Ace on this one. There are a lot of antennas on the market (no matter the hype, no matter the popularity, no matter what), that in reality, aren't what you might say, are breakfast of champions! Sure, they work, but no one seemingly defines what work means! The MA6V is in that category. Assuming you put it together like MFJ suggested, and you checked the SWR at the resonant points you set it up for, then perhaps the LDG might allow you to QSY from those resonant points at least a few KHz away. If on the other hand you assumed the LDG would handle whatever impedance the antenna threw at you.... you've jumped off the pier!
This specific antenna presents a rather large amount of common mode current. That is why there is specific instructions included about winding the common mode choke. Even then, there is still quite a bit of CM to deal with. Depending on the length of the coax feeding the antenna, you may, or may not, experience problems. Apparently you are.
Again, assuming you mounted the antenna like MFJ suggests, you need to measure the input impedance (sans the LDG), to see if it is even close (at the antenna, not at the shack end of the coaxial feed). I'd bet it isn't. In fact, I suspect the resonant points are way off from what they should be.
It is unfortunate, that today's amateurs have to buy additional hardware (i.e.: MFJ-259B or similar antenna analyzer) to make sure what the manufacturers say in their manuals is correct. Oh! This is yet another case where an SWR bridge is almost worthless.
Alan Applegate, KØBG