I feel your pain. I had an Aventa LX and base plate on the Sivlerado toad that gave me no end of problems while in Alaska this past summer. I installed the base plate myself EXACTLY in accordance with Blue Ox instructions and using all necessary Loctite while torquing to specs. Regardless, the attach bolts started to thin out the Chevy box frame, elongate the holes and actually crack the frame in 2 places. I ended up having to re-tighten the bolts at the end of each day's run and completely remove the base plate when I got home. After thoroughly inspecting the attachments, I believe the base plate did not have enough strength where the bolts penetrated the frame. Very heavy washers under the bolt heads and nuts were required and not furnished. This resulted in high loads that thinned the frame and allowed the attach bolts to loosen, and subsequently elongate the bolt holes. It became so loose on my rig that it also caused the removable "tabs" to bend.
I completely documented the damage with pictures and explanations and after calling and talking to Blue Ox engineers, sent them the pictures my findings and conclusions. Blue Ox was singularly unimpressive in their response. In fact, they refused to accept any responsibility or to pay for any repairs.
I redesigned the attach setup with 1/4"x2" bar stock for backing plates and with the help of my local welding shop had the new pieces welded to the frame and the cracks properly repaired. We have had no further problems.
When I first started towing 4 down a number of years ago, I was very impressed with Blue Ox tow bars and base plates. I had the tow bars replaced between 70,000 and 80,000 miles and the base plates closely inspected on a continuing basis. Up to recently, I was completely satisfied with their products. However recently I have seen a marked decrease in their product quality and workmanship. I am now seeing excessive tow bar wear in the LX knuckles and excessive wear in the areas where pins and bolts go through their castings. This wear is so bad that I have begun to use steel shim material to tighten up numerous connections. Furthermore, they have overtightened a number of set screws to the point where they strip the hex key sockets so the screws cannot be removed for tow bar maintenance. Although I tow a large number of miles I have the towbar inspected and repaired by Blue Ox when necessary annually at Quartzsite
Too bad, really. Blue Ox used to be a good company that produced quality products. I'm afraid that's no longer true, and I have no intention to continue using their stuff in the future. I'd also recommend others look closely at their choices before choosing Blue Ox products.