Cathode output for 8 and 9 wrong

[graphex]

I have a problem with my tester where it cycles through the cathodes in the order: 1234567010 and then repeats starting with 1 again. It never gets to the K8 or K9 pins, and the manual push button follows the same sequence as the auto mode. I've put the socket on a breadboard and when I connect K8 and K9, the tube properly shows the numerals 8 and 9. This is consistent whether I'm using the Socket No. 4 (IN-18), 9 (IN-14), or 18 (IN8-2), or using the outputs on the front. Any ideas how I can troubleshoot and hopefully fix this?