The iPad cannot be synced unknown error (-54), stopping just after started step 4

Itunes 12.5.5.5

MacOs 10.12.3

iPad Air MD793NF/A

The iPad cannot be synced unknown error (-54), stopping just after started step 4, during sync with an updated of one of my iBook bought on the store.

Because i have 2 iTunes account, one french, one canadian, i have regularly some difficulty when i want to sync my iPad on my Mac.

So I try to identified at what time exactly the sync stops, for this specific case it was during the sync of this iBook. The iBook was up to date on the mac but not on the iPad »

Then, i went to the iPad, move to the right Itunes account and update the book. It was really difficult, because i have to click many many time ont the « update » button to make it start.

Last time, but it appends very often, It was an app, up to date on the iPad, but not on the mac, then, I have to identify which one, and update it before on the mac to avoid crash during sync.

Sometimes it looks like there is too many apps to update, not enough memory to do it ???

I already totally erase my iPad and use my last backup without any amelioration.

Unfortunately, removing the issue with iBook was not enough, Apps sync doesn’t work, I have a bunch of apps updated in my iPad but not recognised as in my mac…. And I cannot see which apps is looking the process…. step 4 starts and stop without info…

APPLE, can you give more detailed information to the end user about problem during sync ???? warning windows with detail ???

After iTunes update in 12.6.1.25

My iPad also deasapear from iTunes…. because it cannot be found…

Same for my Iphone

No change.

In short…a nightmare. Now Itunes is stuck synced an upgrade of Facebook on my iPhone….

Argh… finally I update all my apps 2 times, one on my iDevice, one on my mac, and now, because there is only one or two apps to sync, it works.