We struggled with a similar issue (PRJ, PR_31, PRB would randomly vanish during payroll processing). Opened several cases with Sage, hit the Tools team a few times. We tried NICs, drivers, A/V, permissions, power management, SMB signing, opportunistic locks, just about everything. Once we moved MAS to a new server, the problem went away, so we never did find the cause. In my case it was a Server 2008 R2 terminal server connecting to a Server 2012 MAS server. They had Abra integration, FAS and BizNet.