For the last month or so, the SEI assembly crew has been trying to figure out the source of a lateral "twist" in our third BSC assembly. When we initially loaded and released the ISI (~ 1 month ago) initially we found an approximately .060" rotation in Stage 1 relative to our nominal position. After replacing the flexures and springs,as well as measuring the Stage 0-1 spring posts for machining errors, we adjusted the springs on their mounts (using available dowel pin slop to rotate the springs to counter the ISI's rotation), we floated the ISI a second time and found a .040" rotation. This is close to what we found on the second assembly (BSC6), but this rotation was enough that we could not connect horizontal actuators. For our 3rd round of releasing the springs, we replaced the flexure brackets and gussets. Measurements of old and new brackets/gussets showed no differences, no off angles on either set. This time when installing flexures, though, we pushed sideways (in the plane of the ISI rotation) on the bottom of the flexure, hoping to offset more of the rotation. It seems to have worked, as we now find ~.007" rotation.