Sometimes under performance is not really about the person, it’s about the job being badly designed.
If you just assume that under performance is the person and you sack them or move them on, you will find the next person fails as well.
If you do a proper performance management process you can find out whether it is the person or the job, and if it is the job you can fix it.
Here’s a tip: If several people have ‘failed’ in this job, is it the job?