this is something I already tried. I use Navicat for MySQL to run queries directly on the final server.
Here is the query I use to make this test:
registrazioni.data_scontrino_reg = '2018-10-03' AND
registrazioni.ora_scontrino_reg = '15' AND
registrazioni.minuti_scontrino_reg = '50' AND
registrazioni.numero_scontrino_reg = '528'
The query results are ok. Some records are displayed. But the validation still (erroneously) pass.
So, the WA validation server behaviour should fail (since $totalRows_rs_doppioni is a number >0).
I attach the WA server validation screenshot related to this check: do you think it is correct?