We're seeing a mismatch between the list of patrons retrieved from the search form that pops up at the time of hold placement and the regular search form.
On demo.evergreencatalog.com with the Concerto data, searching for all patrons named 'smith' pulls up 11 patrons on the normal search but only 10 in the search at hold placement time. The patron Jane Smith will not come up in the pop-up search either by name or by barcode (12345) although if the barcode is entered directly into the 'Place hold for patron by barcode:' box then it retrieves with no problems.
With a larger data set like ours, this is even more problematic - searching for patrons with the last name Keane in our database, for example, pulls up 61 patrons in a regular search, but only 28 in the pop-up search.
I noticed that Jane Smith has CONS as her home library. Is it possible that it's not displaying patrons whose home library is not an eligible pickup location? I'm not saying it's a good thing, but just trying to pinpoint the problem.
In the example that used production data, it seems unlikely that 33 of those patrons have a home library that is not a pickup library. Have you verified that all the limiters are the same? When I use this feature, I keep forgetting to change the scope of the search to the entire consortium. Include inactive is another one that sometimes trips me up.