Here we go, the log file is a mine of information

It seems the machine started up fine, ran fine until 2016-10-02 | 09:52:21.375 where we get the first "Software limit switch activated!" error - this would be when it sent the Z axis home for a tool-change.
So, as i said, its not a real limit switch thats getting hit, its some sort of software limit.
Its also the Z axis throwing the following ePid fault - 2016-10-02 | 09:56:24.625 -> ePID Fault on Axis(2) : FAULT
Question is - why?
2016-10-02 | 09:17:24.718 -> CSMIO-IP class initialized OK.
2016-10-02 | 09:17:24.734 -> InitUDPSock -> OK.
2016-10-02 | 09:17:24.734 -> piInitControl: Module filename: C:\Mach3\PlugIns\CSMIO_IP_A_plugin.dll
2016-10-02 | 09:17:24.734 -> piInitControl: GetFileVersionInfoSize = 1716
2016-10-02 | 09:17:24.734 -> piInitControl: ProductName: CSMIO-IP-A Mach3 plugin
2016-10-02 | 09:17:24.734 -> piInitControl: ProductVersion: 2.8.5.1
2016-10-02 | 09:17:25.687 -> Our IP address : 10.1.1.1
2016-10-02 | 09:17:25.687 -> Our subnet mask : 255.255.255.0
2016-10-02 | 09:17:25.687 -> Calculated broadcast : 10.1.1.255
2016-10-02 | 09:17:25.687 -> Sending discover message to broadcast.
2016-10-02 | 09:17:26.359 -> All network interfaces checked...
2016-10-02 | 09:17:26.359 -> Discover finished. Found 1 CSMIO-IP device(s).
2016-10-02 | 09:17:26.359 -> Connecting to CSMIO-IP at IP:10.1.1.2
2016-10-02 | 09:17:26.359 -> Connected.
2016-10-02 | 09:17:27.109 -> llComm(c:45): Rx time-out. retry = 0
2016-10-02 | 09:17:27.109 -> llComm(c:45): NAck with nackTRREP received. (no retry).
2016-10-02 | 09:18:05.171 -> Sending reset to idle state request.
2016-10-02 | 09:18:07.218 -> Homing start axis:2
2016-10-02 | 09:18:12.296 -> ClrAxisPos: Axis:2 / DeRef: NO.
2016-10-02 | 09:18:12.296 -> Axis 2 homing ok.
2016-10-02 | 09:18:12.359 -> Homing start axis:1
2016-10-02 | 09:18:15.546 -> ClrAxisPos: Axis:1 / DeRef: NO.
2016-10-02 | 09:18:15.546 -> Axis 1 homing ok.
2016-10-02 | 09:18:15.640 -> Homing start axis:0
2016-10-02 | 09:18:22.515 -> ClrAxisPos: Axis:0 / DeRef: NO.
2016-10-02 | 09:18:22.515 -> Axis 0 homing ok.
2016-10-02 | 09:52:21.375 -> Software limit switch activated!
2016-10-02 | 09:52:58.843 -> Sending reset to idle state request.
2016-10-02 | 09:55:34.437 -> Software limit switch activated!
2016-10-02 | 09:55:42.453 -> Sending reset to idle state request.
2016-10-02 | 09:56:24.625 -> ***********************************
2016-10-02 | 09:56:24.625 -> ePID FAULT! (State = 105)(Alarms=0x00000002)
2016-10-02 | 09:56:24.625 -> (ThreadSt=5) (RTappSt=0)
2016-10-02 | 09:56:24.625 -> ePID MaxError on Axis(0) : 156
2016-10-02 | 09:56:24.625 -> ePID MaxError on Axis(1) : 1
2016-10-02 | 09:56:24.625 -> ePID MaxError on Axis(2) : 681
2016-10-02 | 09:56:24.625 -> ePID MaxError on Axis(3) : 0
2016-10-02 | 09:56:24.625 -> ePID MaxError on Axis(4) : 0
2016-10-02 | 09:56:24.625 -> ePID MaxError on Axis(5) : 0
2016-10-02 | 09:56:24.625 -> ePID Fault on Axis(0) : ok
2016-10-02 | 09:56:24.625 -> ePID Fault on Axis(1) : ok
2016-10-02 | 09:56:24.625 -> ePID Fault on Axis(2) : FAULT
2016-10-02 | 09:56:24.625 -> ePID Fault on Axis(3) : ok
2016-10-02 | 09:56:24.625 -> ePID Fault on Axis(4) : ok
2016-10-02 | 09:56:24.625 -> ePID Fault on Axis(5) : ok
2016-10-02 | 09:56:24.625 -> ***********************************
2016-10-02 | 09:56:34.296 -> Sending reset to idle state request.
2016-10-02 | 09:58:19.750 -> Sending STOP request.
2016-10-02 | 09:58:19.812 -> ***********************************