My guess would be programming bugs. I think I have seen this.
Ever since they messed with the osnaps in acad, adding 3dosnap etc there have been problems with osnap to aecobjects. My take was that it had to do with layer 0 being off and where componants thru the style or material settings were mapped to, (check the section style). Others seemed to think this wasn't their problem.
I could verify this was my case but now in 12 it's just random and sometimes can only be solved with a restart.
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