Issue resolved. New gauges did not fix it.

I replaced the instrument cluster enclosure and everything worked.
When I put back my renewed enclosure (which had the front glass knocked out and glued back), the issue came back. However, I wiggled it a bit in place and everything works now. It seems that the curvature of the enclosure affects pressure on ground points or something. It is weird, but it worked. It's not a mechanical issue related to the flexible shaft.

Just in case someone encounters similar issue.

__________________
*** I can unlock your Becker 754/780/1492, add aux/bluetooth...