What you may be seeing is the dreaded orange peel which spinel happens to be prone for that. For one thing I never use a 1200 lap on this stuff but rather go directly from my 600 sintered to something higher like 3000. For some reason that seems to avoid the problem. If you do encounter orange peel you have to back up in grit size. For example encountering it at 1200 you have to go to 600 and recut or waste a lot of time. Pits resulting from bubbles is unlikely in sync spinel. Keep at it. Spinel cuts beautiful stones a good seller for me.
Jim Foster
Santa Barbara