I was using one of the 4702 stanchion blocks, similar to this one:
Given that I had a sprained wrist at the time and a wrist brace on.. and three of the four screws tightened up just fine, and the last one pulled free without even me straining... I seriously doubt it was my "overtightening" it. I didn't feel the block would work under the loads required of it with just three of four screws holding it in place, since they are the only things holding it to the stanchion. I stand by my previous statement—the stanchion mount on these blocks are a piss-poor design and Harken knows it.