Classic USB SNES Controllers

My buddy and I each purchased two USB SNES Controllers.  A few of my friends got together at my buddy's place to place some classic NES and SNES games on emulators.  When I got there, he told me that the SNES controllers had some bad reviews.  Given how cheap they are, they had manufacturing problems.  At this point, I was already using one of my controllers for a few weeks.  He said that most of the defects could be fixed by taking the controllers apart.  At first, we didn't notice any problems.  We were playing Bubble Bobble with ease.  We noticed the problem after we switched to Dr. Mario.  On one controller, the down button also moved right.  My buddy took it apart just to discover that a screw was missing.  This screen held together the left half of the housing.  Without the screw, the internals slid around a bit.  This caused the D-Pad rubber to misalign.  He was able to fix the alignment, but the screw was still missing.  The down-moving-right problem went from happening 90% of the time to 5% of the time.  For most games, that is not that big of a deal.  For Dr. Mario, it is a definite handicap.  I have not experienced any issues with the one controller I have tried, but I haven't played Dr. Mario either.