The right bolt in the Playing the Slots anchor has been loose for some time and the vertically offset configuration of the anchor has never been ideally configured to equalize the rappel. Originally the anchor only had a pair of quick links, creating a rope kinking rappel station. Last year I replaced the corroding plated steel links with stainless links and rings and tried to clean up the hangers.
Since the bolts were 5-pieces (which have a poor track record in schist) I decided it was probably just best to remove them and replace with glue-ins. In the process I found that the bolts were plated steel mixed with stainless steel hangers. While they looked okay on the outside they were corroding inside the hole; far from ideal. The most disturbing finding though was that the right-hand bolt (which was perpetually loose) was assembled incorrectly.
The 5-piece bolt is named for the 5 pieces that make up the bolt; the threaded bolt, spacer, plastic compression sleeve, perforated expansion sleeve, and the cone. The correct assembly slides the spacer on the bolt first, followed by the plastic compression sleeve, the expansion sleeve and lastly the cone. The expansion sleeve must but assembled such that the perforated triangles point towards the threaded end of the bolt (and the cone).
The right bolt was installed with the expansion sleeve facing the wrong way. So as the bolt was tightened down the sleeve expanded up past the compression sleeve and spacer and deformed around the edges of the bolt hole. This was the reason the bolt hanger was perpetually loose.
These bolts have been replaced with stainless 12mm glue-ins and all stainless hardware.