[Plugin: WP-Stats] Top Posts Failing

When I visited my dashboard today, the area of the stats panel that says “Top Posts” was blank, and the area that says “Most Active” listed only two old posts (each of which hasn’t had many views recently). Yesterday, the both sections were normal, each listing about 5 very popular posts. I actually first noticed this problem because the WordPress Popular Posts plugin started failing, but I don’t think there’s any problem with that plugin.

A possibly related issue is that https://stats.wordpress.com/csv.php is giving me some unusual and inconsistent (!) output when I set both the “summarize” flag and specify a “days” parameter. For instance, the options “api_key=[mykey]&blog_uri=davidsd.org&table=postviews&summarize&days=2” give the output

post_id,post_title,post_permalink,views
1,Hello world!,https://davidsd.org/2008/12/hello-world/,10
2,About David Simmons-Duffin,https://davidsd.org/about/,9
3,Culture,https://davidsd.org/culture/,6
,,https://davidsd.org///,5
5,Theorem of the Day,https://davidsd.org/theorem/,3
6,Theorem,https://davidsd.org/2008/12/5-revision/,3
7,Philosophy,https://davidsd.org/philosophy/,3
,,https://davidsd.org///,3
9,Things by Which We are Amused,https://davidsd.org/amused/,2
10,Amused,https://davidsd.org/2008/12/9-revision/,2
11,Hello world!,https://davidsd.org/2008/12/1-revision/,2
12,Honda Needs a Tune-Up,https://davidsd.org/2008/12/honda-needs-a-tune-up/,2
13,Honda Needs a Tune-Up,https://davidsd.org/2008/12/12-revision/,1
14,Honda Needs a Tune-Up,https://davidsd.org/2008/12/12-revision-2/,1
15,Honda Needs a Tune-Up,https://davidsd.org/2008/12/12-revision-3/,1
16,Honda Needs a Tune-Up,https://davidsd.org/2008/12/12-revision-4/,1
17,Honda Needs a Tune-Up,https://davidsd.org/2008/12/12-revision-5/,1
18,Honda Needs a Tune-Up,https://davidsd.org/2008/12/12-revision-6/,1

I’m not sure if this is normal behavior, but the following things struck me as odd:

• inclusion of multiple revisions for the same post
• view counts incorrect, even after summing over revisions (for instance, “Honda Needs a Tune-Up” has had 255 views over the last 2 days, and “Hello World” has had fewer than 10)
• multiple entries of the form “,,https://davidsd.org///,5”. The triple slashes after .org suggest that this isn’t meant to be for the top level. Are these posts without names?
• different types of responses at different times and with different day counts: Most day counts always give the funny behavior shown above. However, when I set e.g. days=10, sometimes I get the funny behavior, and sometimes I get normal output! It changes from minute to minute, and I haven’t discerned a pattern.

My guess is that WP-Stats and stats.wordpress.com/csv.php are doing the same database queries, so funny behavior in one is being reflected in the other. Is this right? Is the source of the problem stats.wordpress.com, or WP-Stats, or WP Popular Posts, or a misconfiguration on my part (I don’t think I’ve changed any settings recently)?