Lead 1515 Z axis keeps resetting Z zero

I am not sure what is happening.
I home my LEAD 1515 (yes I have the Lead 1515 loaded in the Touch)
I probe to zero the XYZ
Here it's probed.

I run the program. It essentially is putting in dogholes in a piece of 3/4" (19.05mm) mdf.
When it runs, the first hole seems to mill properly at the top where it dives to the center where z=0 and starts milling in circles. The problem is it is supposed to go down to 19.15 (3/4" +.1mm) and it's not. It's going down to a little more than 13mm and coming back up to the next hole.
Here is the measurement of the first and second hole. It should be about 19.15mm

The next hole is supposed to dive back down to z=0 again as per the instructions but it is doing it about 5mm above where it's supposed to.
I cancel the operation and send it back to XYZ zero and it is no longer touching the stock. The physical Z does not match what the Touch says is the Z anymore.

But is about 5mm higher than what I initially probed. Here I drop it back to what Z SHOULD be and we see the 5mm difference.

This is the approximate difference between how deep the hole should have been and what it is. I am not sure what gcode would reset the XYZ zeros in the middle of the first hole but something is up and I can't figure it out. I have done more complicated designs with this machine than making dogholes. I have included the gcode created from fusion 360.
I did see something in another thread where they suggested that my z-axis lock collar may be loose. It's not plus I would think if it were it would have a random difference but it's 5mm every time. Any ideas would be welcomed.

 

well I ran another job 8 times that predrilled 12 screw holes, 4 insert holes and carved out a handle with no issues. I thought maybe 10% boring cut grade might be too aggressive (I don’t think so, it’s mdf) but when I run it to test, it is going through the motions of an already cut hole so there is no resistance. It says it’s going to 19mm which is the full thickness but is only going to 13mm. I would think if something were loose, it would have a harder time going up, this is resetting the a to 5mm higher than what I originally set it.

 

The one that works (Basic) uses a 1/8 inch bit. All in one job, it first does 4 pocket boring holes on the corner for inserts, then 12 drills holes for eventual screws for the hinges and then cuts out a shape for the handle with a 2d contour (does it in 6 passes to get through the 19mm thick mdf because I don’t want to break the 1/8” bit)

the ones that seems to reset the a z after the first hole (MaxDogholes or TrayDogholes) is just supposed to bore out 3/4” dogholes every 4 inches. I change to a 1/4” bit for this job.

Fusion

 

Maybe instead of boring out the dog holes, I cut them out with the same 1/8 bit in passes

That was my first thought that the bit was being pushed in but it didn't appear so. I'll go back and tighten everything up on the gantry. Thanks for your insight.

 

Well to close this out (I thought I replied with the solution to the issue but it didn't post)... I disassembled the z-axis to figure out if something mechanical was going on. It turns out I had taken off my dust shoe before these carves and had my router position not in its usual spot but installed just high enough that when it went to the programmed depth, it was barely bottoming out causing the tension nut to spin but not go anywhere. It was barely one click so I didn't hear the normal grinding sound but it was enough to move so that it thought it was going deeper than it was for the next hole and it required running through the entire recalibration. I didn't have issues with one bit because it was a half-inch longer than the other one. I adjusted the router a half inch lower and it started working as intended.
Thanks for the suggestions that helped me find my issue.