There are essentially two issues with the Bachamm Big Hauler couplers. First is the mounting. Out of the box, the couplers are mounted to a tang/tongue (depending on your favorite term) on the truck. This causes the coupler to ‘droop’ and not be stable. This is not terrible if you are only pulling the cars in operation. If you are doing switching operations, they get much more likely to cause a derailment if you are pushing more than one or two cars. Switching to some form of body mounting will aid this issue greatly. There are several threads on body mounting the standard Big Hauler couplers.
Second issue is in the coupler itself. MY SOLUTION was to carefully disassemble the coupler. There is a small spring that opens the knuckle, make sure to contain it when you push the pin out of the knuckle. Carefully, using a sharp (said new) Xacto #11 blade, clean all the flash off all the mating surfaces of the three operating components (knuckle, body, and drop pin). Pay close attention to the drop pin. Sometimes the plastic does not form quite perfect and you will get a high spot. Again, carefully with a fine file or emery board flatten the high spot. I DO NOT RECOMMEND any form of lubricant, wet or dry. Carefully reassemble the coupler and it should perform considerably better. Be prepared to spend some time if you plan to do it right. Doing them in mass will speed up the process, but I found keeping the parts to each coupler together seemed to be more reliable. Doesn’t make sense, but that was my experience.
All of that said, I have been on a slow process of converting to Kadee ‘G’ coupler, which play quite nicely with the Big Hauler couplers. One transition car allows me to mix and match body mount Kadee, body mount Big Hauler and truck mounted Big Hauler couplers.