"Is there anything elastic inside? I believe that if there is, it makes the flow impedance (clog) and accumulates pressure."
nah nothing elastic inside, sonds like your hitting off a piece of unmelted filament..
I'd be looking to dissasemble it myself , but i have a spare couple of nozzles exactly for this scenario, i can change straight away and then fix the blocked nozzle...this in itself can take a few days as i generally soak the nozzle in acetone for a day or even two prior to cleaning it.
I also dissasemble the nozzle from the acrylic extruder/stepper motor, then simply reconnect the nozzle assy with the two wires to the wiring loom and and leave it suspending in air.. then i just heat the nozzle up from RH...once it gets to about 100 degrees, i gently pull on the filament to pull it from the barrel... you dont need to pull too hard, but it needs to be done before the plastic melts... you end up pulling out a single complete soft piece of ABS the dia. of the barrel..if your timing is good, it should by in large come out in one piece, leaving only the nozzle to be soaked overnight.
works for me so far!