Queries just do not run occasionally?

My first user/tester is reporting that some dropdown will not be populated with any data. It seems random and intermittent. A page refresh will fix it most of the time, but other times she has to wait a few minutes and then refresh. She does not see any error messages so I do not know if the query failed from the server, or the query worked but the dropdown did get "linked" to the results or what. And since it is not happening to me I am a bit stuck on debugging it.

Here is a screencap she sent me. She is using Chrome on a Macbook.