It's worth separating your post out into two parts @nicholas.shen
If clubs are able to offer higher wages, higher squad status then even at the elite clubs you will find players potentially getting their heads turned. It does happen, and you have more tools at your disposal to mitigate this. A player being unhappy about not getting a move isn't the end of the world. If you put yourself in a strong position you can simply wait this out, integrate them at your own pace and it will usually work out positively. There's no guarantees, different player personalities and the likes may make selling better in the long run.
You will find you can wield this same influence over others though.
In particular with this instance though, if you have any save games of a deadline day where this is happening our QA team have identified they would like to look into further. If you can create a new thread about this should it happen to you again then its an area we definitely want to look into some more.