Lost ESS data in the middle of a cut

4 minutes into a cut, ESS data totally dropped, last Goto code still going, but shut down spindle, which resulted dragging bit across material. Cannot get Mach 4 to communicate with CNC anymore? Anyone encounter this snafu?

When you do get it going again be sure to set this up (see pic) this will prevent dragging the work piece around if the spindle stalls. It will send a stop code to the vfd which sends an E-stop code to the controller.