That bolt....on the picture before reminds one thing long ago. O-rings on Cetop-valves needs to be quite right and servo valves needs to be mounted pretty much right torque or the spool does not move reliably. On one setup we had problem of oil seeping on valve stack. Checked it once and doublecheeked shema and measurement....should be fine, but it's not fine. Then I checked and measured the bolts...fine, but ends had a slightly crushed thread.....what rhymes with a clacking bell? The threaded holes/threads were just too short (shorter than spesified) and some innovative cad user had reenginered the valve block thread upon on catalog bolt/stack height. Crapity crap! No thin rider/dummy block to mach next longer bolts, needed to get innovative with the bolts and order a new valve block, can't just leave someone else to find what's wrong with it.
For an electrical engineer hydraulics is weird sometimes, because if you can't trust the schema and you can't trace the pipes/hoses you are left armed only with your vivid imagination.