Convert to symbol cause desynchronization in animation

I follow with a little box animation history, but when I convert crane elements in one symbol, then nowis not synchronized withthe box movement whenthecrane liftsthe boxand takes herto the leftafter raising. It is a smallbutnoticeablelag, in previous version when symbol crane not was create (allelementsweregrouped intostage) the synchro was perfect: dissenys.cat/practice/caixa.html

Edge project just before convert crane elements to symbol: app.box.com/s/m5ful0jb0ydiovktw0gc (263.9 KB)

I have reviewed timingandaccelerations (easings) and are the same asbefore.What can happen?

Note: if I convert crane+box to symbol, then the eyesare out of sync, and if I convert crane+box+eyes then works fine. But I don't understand why if I convert only the crane elements to symbol, the box and eyes are out of sync respect crane symbol.

Thank you.