Monito,
obviously my guess on the programming was wrong :p
assuming you have too high of a fill level in the boiler and you have such high pressure that the 3 way solenoid on the headgroup leaks during a shot consider this:
one of the tubes somehow goes from pump to boiler by way of a solenoid. (in your pic 40 right rear is that 2-way solenoid) The state of that solenoid controls whether the running pump also fills the boiler (or just provides pressure to the grouphead lines)
The solenoid (3way) near the grouphead can decide whether water goes to your portafilter, to the dump or neither. That is its 3 wayness :p
If you manage to see boiler level in your sightglass (ignore the stuck ball but leave front panel off to see the entire sightglass), do the following test:
1.) trigger pump by activating manual dispense
2.) maximally restrict flow through grouphead with fine grounds or with blind disc. (pressure is altered this way not just on vibe pumps, but ALSO on rotaries)
3.) let this run for several minutes and whatch the boiler level through your sight glass. Does it rise at all? ( I know i know busted HX and that. The HX on that machine is pretty indestructible. it won't be the fault. if the HX were indeed busted the level would rise crazy fast while pressure during shot would be weak at first and then skyrocket as boiler fills)
I am not sure on this, but maybe crholliday knows for sure.
Pic 44 lower right near astoria badge. looks awfully like manual boiler overfill circuit.
Those work via 2 springs opposing each other and a little plate that can route pump pressure 3 ways. Those gum up universally on all espresso machines. you might have to take that apart and clean it.
if you have water leaving our 3-way solenoid during your lengthy shot thats probably just scale...
Since you also had the "pressure goes up nothing moves" experience, chances are really good that all you are experiencing is scale messing with either solenoids, boiler float or both.
very nice machine.
Felix
PS: on setting pressures and shot lengths. crholliday is right about HB. they have endless threads with endless detail. (Going very far on the lower end of boiler pressure will save you flushtime and $. With home volume these commercials are just so underwhelmed that they do not need the higher temp and boiler pressure they do in a cafe.)
PPS: someone rebuilt a Rio version of your machien on HB, that might have been holliday. i am not sure.
