I had a simple to diagnose case today, with it being the first day of the week and me hitting the rep cap very early. Before going to sleep, my rep report was showing 3 posts marked as the answer and a bunch of upvotes that exceeded the rep cap. Reported score on the /users page (week view) was 230, 15 too few.
After a fitful sleep, 10 hours later the score was still 230, a handful of additional upvotes added that didn't count. Far too long to explain the problem away with caching I'd think. About an hour later, another post was marked as the answer. The /users score incremented to 245, still 15 too few. Looks like the rep for one of the 3 answer marks got permanently lost.
Something to help with debugging this: the three marked answers were one, two, three. The late 4th mark that incremented the score to 245 is this one. I'm not aware of anything special with these posts. The /reputation report looks like this:
2 5207104 (10)
1 5207104 (15)
2 5202207 (10)
2 5206571 (10)
2 5208433 (10)
2 5206797 (10)
2 5208433 (10)
2 5208433 (10)
1 5208433 (15)
2 5208433 (10)
2 5207512 (10)
1 5202207 (15)
2 5208433 (10)
2 5206571 (10)
2 5205773 (10)
2 5204859 (10)
2 5208879 (10)
2 5208879 (10)
2 5208879 (10)
2 5208879 (10)
2 5207964 (10)
2 5209032 (10)
2 5209032 (10)
2 5207330 [0]
2 5208596 [0]
2 5209032 [0]
2 5206571 [0]
2 5208433 [0]
2 5197010 [0]
2 4642034 [0]
2 5182256 [0]
2 4940225 [0]
2 5208433 [0]
2 5208596 [0]
1 5207330 [15]
2 297061 [0]
2 1702625 [0]
Good luck!