Hi folks,
First I would agree, I did not seem to have this issue with 3 either. I had a very hard time swapping but I did it. There is a ton of control you have in 4 that you need to be a computer smarty to understand.
I do not have an estop on this machine (I should I know) but I really do not feel I need one. I use MACH4's Stop on the main screen. I often use the Feed Hold with no issues and if I am cutting something like plywood and have to stop suddenly then this seems to happen BUT not always.
I also have this machine earth grounded. The panel is grounded back to the main box that is also hooked directly to earth and then I also have the gantry grounded. Not saying your wrong by any means but this seems repeatable, and I really have no other issues.
They only time I really use this is when I feel I ran the CAM wrong or if a part slips but I always keep the same G54 so I do not need to reset the work home as it doesn't change.
Again, I use the stop that is in MACH (pic attached).
I am by no means a computer expert, but this does seem like a glitch?? I would be happy to check anything

Hi. Thanks for that. In my case it didnt pose a large problem until I installed a 4th axis which is a whole lot more to setup after losing position.

Mr Rufus your problem appears to be similar to mine abet more pronounced. But do look at your fixtures, parts moving is the worst, and as you progress if you upgrade your machine as I have done, its a large piece of aluminum that might decide to make a hole into something if it lets go. Timber, well I put a 200mm machined ball into the opposite wall off my lathe that was a fun day. The dent remains.

As mentioned its a problem for me if in the rare occasion I need to stop urgently. I am running close to the line on momentum with the largest Nema 34 I could find. A side business for me its all about time taken to machine so I do push the limits. Occasionally on a very aggressive run my Nema will lose its position and E Stop the machine, this is also untidy similar to hitting the buttons. Although, the stop button is the worst.

Earthing is an interesting subject and I am going to look further into my machine. My case, if I hit the stop button, the machine will stop immediately, then about a split second later I will see it shudder which is the problem. I can only think a surge, can only be in my mind. Back to earthing, I am electrical worker in cardiac so know a bit about it. If you have any shielded conductors in your system, and have connected both ends of the shield to earth, its plausible a ground loop will be created making the whole earthing process moot in that conductor. Not sure in your case but I am going to check those for a start there is a lot of room for noise in a cnc controller, and its a simple mistake.

I think also about me I am going to look at an estop relay, cant say I have ever seen or installed a specific one prior so thanks for that Mr Byrd. BTW I never look at sites but did look at yours. Super cool, my workshop is mostly joinery, I have designed a bunch of window/door tooling and automated several of my machines including a tennon machine. Although my router is not capable for large steel components.

Mach 3 to Mach 4? I had no choice I started running out of IOs, so took advice and upgraded. It was a package deal with the ESS. Still using Mach 3 on my lathe though its robust with XP.

Thanks for checking it out!  We like what we do.
We use mach4 because it runs so much better. We use a PLC to handle the majority of our IO.

Just a small update and a few questions. I had left Mach on for a couple days straight. I came in and was going to us the router and noticed that the program had shut down, but the panel was still live. So, I decided to reboot everything just in case. I started everything up and did a homing sequence and Z did not stop however it did record on Mach screen that Home was triggered. What actually stops the motor when home is triggered? 1 other thing I would love to understand. When I turn on my safeties, I can no longer run the home sequence as the machine will trigger the Z switch and then stop on limit switch fault. Am I missing something in the setup? I thought when MACH is asked to start the Machine Home sequence it bypasses the safeties and continues to the next steps, Z,X, then Y home. Once that is finished it then recognizes the safeties or am I wrong?

I had to reboot 2 times and then everything worked as it should.

Homing is controlled solely by the motion controller.  So you may need to restart your motion controller.  I had to do this when I used the Smoothstepper.  I haven't really had to do that with the HiCON.  Maybe try powering that off and try again.
I do know that you can double up your limit and home switches, I did this on a bridgeport series ii.  It would ignore the limit switches while it homed and then once it finished homing it would look for the limits again.