Guys, in first I am really happy about your interest and help.
I very carefully read the last BartS and bsft messages and I taked a lot of points of interest.
But unfortunately I find the problem.. and yes, it's my fault.
Just all these months of work and my attention slowly fall and I forget to set ON in the "input disconnected" and "feedback disconnected" error page of the jrk config utility precisely for the motor that went mad.
(I modified to OFF these options, one week ago for some tests and never forget to re enable...)
Each other 2 motors have these options enabled but just now I noticed that the left motor jrk have these 2 options disabled.
I think if these options are disabled then is normal that If the motor exceeds the pot abs max level nothing will brake it..
I do not know how I could forget this fundamental security step.. I know just this has happened.
if I had enabled these securities options from jrk config utility so I have gotten just the motor position over the abs max then the motor stirrup stopped before to make damage.
But both the security options was not enabled.. and bye bye.
Probably I need a bit of time of relax and "shut-off" from my project, or just to use more relax and operative way to continue to work.
I can not really afford these expense damages..
From a side of this sad discover, this is a good thing too because now, probably, we know WHY this is happen and no more fear about strange jrk behaviour.
Just a damn my error.