hello Mr. M,
I have solved the problem.
I try to let the computer which been installed M monitoring software using the core network switch port VLAN assignment.
All problems solved, 51 seconds to scan 1,200 ants mining machine. One second refresh time.Refresh cycle time is 1000s.

I guess it should be out in a soft routing firewall, the packet may be too large to scan M monitoring,
Because I saw an instant network uses 10Mbps. Firewall denied network access
Mr. M, sincerely thank you, great software. best Wishs