This has to be viewed as 'Conflict Resolution'. When new developer doesn't fit with existing members, it has to be seen with respect normal cycle of forming - storming - performing, etc. Even after that cushion is given, if scrum master sees that there is some conflict, the best approach would be to discuss with all members including the new employee. And Scrum master must ensure to play neutral and shares his/her feedback to respective next level.
Normally, there will be multiple scrum teams. If one employee doesn't do well in one team, he/she may do better in other team.
In a better Performing scrum team, most of the deliverable work well because of better chemistry within the team. If something doesn't go well, Scrum master must takes initiative step to resolve as this conflict impacts the performance of the team. But, removing employee from the team may not be solution. It must be discussed within the team as open & heard-out voices of the team members.