GT_eh wrote:
Are there any limits on the number of songs ( I do have almost 35000 songs).
Only the amount of storage available on your phone.
There has been an issue with iTunes for some time now, whereby random songs are not copied to a device. Various work-round have been suggested, such as modifying the non-syncing tracks and trying again. However, as you have found, even a basic second sync (without modifying the tracks) results in a different selection of tracks not being added to the device. Some that made it first time then get mysteriously missed off (removed) by the second attempt.
I just keep trying in the hope that I get a full sync at some stage.