Intermittent connection problem why AOS scans the End User port

We have a issue here ,where there was an intermittent connection problem that ERP cannot be accessed by End Users for one hour weekly once on random basis…

I earlier thought that some symantec antivirus problem which blocks the port from endusers from accessing …

"Why Axapta doing the port scan on User’s machine".

I am not sure why ERP has to do a port scan as random check if the connection is lost or

…Is it TCP IP port check Is it a routine check ?

why AOS scans the End User port

Note:-

I am able to access the ERP from domain A …There are few users able to still access from Domain B,but most of the users were not able to .