Can high contact resistance be repaired?
A contact resistance increase when relays are used in a Dry Switching mode (<10 uA, <10 mV) is a common relay problem.
A contact resistance increase that is caused by dry switching will also be unstable. A good contact will have less than 100 mili-ohms of variation when switched and measured five times in a row.
The solution requires the periodic application of both voltage and current which will clean the contacts. A cleaning procedure using a voltage of 10VDC, that is current limited to 120mA and switched at least 10 times may refresh the contacts.