Connection Issue

I am 3rd party IT for a small business that uses GoToMyPC for remote access.  This client is experiencing intermittent connectivity issues to their host PCs located in their offices.  It seems that this problem is upon "reconnecting" after being connected and logging off.  To me, it is as if it isn't actually releasing it's connection.  They try to "connect" via their account on the web, it shows the PC as available but then timeout and then shows "connected" as In Session and they cannot connect.  Upon restarting the host PC at the office, it may show the option to connect, but it will not.  Other times, the reboot fixes the issue.  GoToMyPC SW is latest revision and these are Win10 PCs with all updates applied.  I have tested this with their A/V Firewall turned off as well with no change in behavior.  There are 5 PCs they connect back to and this behavior has been experienced at one time or another on almost all of the PCs.  Suggestions?  I can connect to them just fine using my support tool - ScreenConnect and the host machines show "online" and no problems.