iR 1110: J0122 when duplexing in A3 size

[Ingranaggio_rotto]

Good morning to everybody !
I have this jam, J0122, on iR 1110 when duplexing A3 size....
In A4 size the machine goes on...
I cleaned the rollers and optical sensors of the reversing unit, but the problem remains...
The machine have 7.000.000 of prints...

Suggestions ?