We have found that a few of our over 25 m/n 34410A & 34411A's have reliability problems when returned for periodic verification, a 34411A on my desk now had a 180 day cal interval and failed 100mV DC, 0.1 and 1K for both 4-W and 2-W (range tests), Zero tests with 4-W shorts are great. I find the Firmware version displayed is 2.40 - 2.40 - 0.09 - 46-09, and the latest update is 2.43, preceded by 2.41. As i read the info presented for these two firmware updates, it doesn't appear that either will help our stability issue. We use an automated Fluke procedure with a 5730A and FGEN for verification, and have an Adjustment procedure that doesn't work as well as manually adjusting it following the manual. Suggestions?