Displayed number of loaned items is unstable

As discussed in a comment on UIU-173, the number of open and closed loans shown for diku_admin seems to change when nothing has happened.

I have created nine active loans. When I start a new Stripes session, go to the Users app and open the diku_admin user, I initially see

0 Open Loans
0 Closed Loans

which quickly changes to

8 Open Loans
2 Closed Loans

That's fair enough – it's classic progressive rendering, showing initial results before the full results are in. But then at some subsequent point, the display changes again to

9 Open Loans
1 Closed Loans

How is that possible? How can FOLIO sometimes think diku_admin has eight items checked out and other times think it has nine? BTW., this is my own local installation I am using here, not folio-demo or one of its siblings – so the answer is not that other people are making changes.

I can't meaningfully work on UIU-173 until this is fixed.