Let me try to answer your post in two parts.
First, I’d like to offer a possible explanation for the two cases of synchronicity you mentioned.
The game: Even though the group of people at the party was a different group from the first one, it’s enough if there is a minimal overlap of people from the two groups, even through a third friend. Now if the game you described is not played too often someone from the first group might have deemed the occurrence important/funny/rare enough to mention it to a friend (who might have mentioned it to a friend of a friend and so on) ... and it made it’s way to the second group.
The song: My first idea upon hearing this was that maybe you didn’t choose to listen to that album by random, and what I mean by this is - maybe you heard a song over the radio, read an article, saw a picture in a magazine that prompted you to listen to those records again, but the trigger was so small, so unimportant that you weren’t consciously aware of it. The people on the bus might have seen the same article, the same picture which again triggered their discussion.
On a similar note, I sometimes find myself humming a catchy tune of a song I wasn’t aware of hearing and then figure out I must have heard it in a shop, or from a passing car. In those cases I didn’t notice the trigger consciously but it still had an effect on me. And there may be even a score of people out there humming the same song, or going through the same association chain!
For the second part of my answer I am entering the area of speculation. You mention that you are suffering from OCD and that the nature and number of those synchronous occurrences exacerbate your anxiety. I wonder whether cause and effect might actually be reversed in that OCD might cause a heightened sensitivity or tendency to look for patterns? I am not too familiar with the detailed implications of OCD (though I have a fair share of textbook knowledge) so I am not aware of any findings related to that but it might be worth to have a look at that.