The RSDCHABAS table did not match our settings in rsa1.
RSDCHABAS showed:
CHABASNM OBJVERS F4DEFAULT F4QUERYEXEC
0FISCPER A M Q
In RSA1, 0FISCPER showed "Values in Master Data Table" for Query Execution Filter Val. Selection, which is mode M, even though the table showed mode Q. That was the problem.
I went into 0FISCPER, changed to mode D (only values in InfoProvider), activated, then changed back to mode M (Values in Master Data Table), activated. That fixed the table entry so it now looks like this:
CHABASNM OBJVERS F4DEFAULT F4QUERYEXEC
0FISCPER A M M