Hi Valerio,
as the symptoms described by the note is identically to the deadlock appeared in my database <SID>.log, i've decided to apply it to my development environment even if my DB realease is 15.7.0.135 and the note validity is for 15.7.0.134.
The result is that since the note application time, i've no other deadlock notifications.
Thanks a lot for your input!
Kind regards.
Massimo Solleretto