Your description seems more like a loose contact in the cabling and not a faulty Reed relay (but I don't rule out a possibility). The best approach is to start narrowing down the faulty cross point using a test circuit.
My technique of choice would be to start powering up a known voltage (current limited by 1k resistor) on one row and connect all other rows to GND, now cycle through each column measuring the voltage, if you don't measure the right voltage, that crosspoint is potentially damaged.
Some additional information ... when I replaced the PXI card the problems disappeared.
The faulty card was repaired, unfortunately I didn't get a detailed error description, so I don't know if it was related to a faulty Reed relay or something else.
Consider if a transient voltage could be the reason and if a varistor or a VRS diode across the reed relay could fix the problems. Does someone have experience with adding some kind of transient protection to a PXI-2532b card ?