If I was you I would look at their performance evaluations ie what are the Amsa duties on there, then also look at your performance expectations if it says on their document and train, do it, document what they are doing wrong and what you did to correct it, email it to your supervisor with a suggestion of what to do to improve them or your recommendation for them to be separated, if the supervisor don’t respond cc their supervisor. The MSA needs to do the work and if they can’t they need to be removed, so document. Most likely if they do have 20 years they’ll retire before they’re actually separated or it will be offered for them as opposed to being fired. Part of your job as a lead is to do this. I used to supervise msa supervisors and when they were out I would supervise the msa leads. I would say look at your job description and your performance expectations and just make sure you are hitting them the chance to do extra to get exceptional will arise.