Today, the problem is back.. not un-expected, because I didn't do anything really.
I found out that the resistance is happening inside teflon tube.
For some reason the plug is formed in the heat-break area (pictured), and that plug prevents the gear mechanism to push the filament towards the hot nozzle..
I just found the discussion about
"heat creep", I suspected something like that, especially after finding that plug in the teflon tube..
Now, why this problem started to appear now? Some of the settings must be in the critical area, and slight variation of something else (environment temperature?) cause the whole process to go to the wrong (or right) direction..