Hi,
The big benefit of mercury relay is that they don't suffer from contact bouncing.
One problem may be that they are not produced anymore (or only in small quantities) because they violate ROHS regulations.
(My assumption, because mercury is a very toxic metal)
Thus you may look for a compromise.
Identical electrical specifications..but with dry contacts.
Maybe - if possible - you need to increase wait time after switching ... before measurement ... in your tester..
Maybe a semiconductor relay is an alternative - without contact bouncing. Like photo-mos relays.
Klaus