Additional information. At 310mm corner to corner, things are good, possibly overlap a bit:

When I jump up to 315, this is what it looks like:

@SlimShader it started with the upgrade to the 3.x branch and having to redo the configuration using the configurator. I'm sure it's something in my config (attached) but I can't seem to find it. I'm going to test tonight to see if it shows up at exactly 300mm.

config.g

@SlimShader I wish that was it. I first thought was that my original FreeCAD model was corrupt, so I redesigned it in Fusion360. I finally just did a 5mm thick block to quickly test where the problem came in at.

It extends on all edges, and even does the same with internal infill after the solid layers. It only starts after 200mm. I just did the math, and it seems it might be when the corner to corner length exceeds 300mm. 225mm square would be 318mm diagonal, while 200mm is 282.8mm.

Any help or pointers would be appreciated. I moved my printer, upgraded to 3.1.1, and changed computers, so a ton of changes. When I print anything up to 200x200, prints are perfect. When I move up to 225 or larger, I get the infill printing beyond the edge of the outer wall. Below is a picture of what it look like. I used the configtool to generate the new configurations for 3.1.1, and everything was working great until I tried to do a print 200x250. I previously printed a 200-250 multiple laptop stand 300mm tall and it worked perfect. I've used Cura and Simplify3D, and both slicers produce the same result. The tool paths look correct, so the only thing I can think of is I missed something in the configuration. Any ideas?

I'm just completing a conversion to a Duet, and I'm seeing the exact same thing. The BLTouch is not in error state (red LED flashing). If I issue:
M280 P3 S10 I1 ; BLTouch Sensor deploy
The probe deploys. Then every time I trip the probe, it extends again. If I issue:
M280 P3 S10 I1 ; BLTouch Sensor deploy
M280 PS3 S60 I1 ; BLTouch Sensor test mode
The probe deploys, Z-Probe value is initially 0. When I trip the sensor, it shows Z-Probe value of 1000.
When I try to run a G32, the probe deploys, and if I manually trip it, it just keeps going down. If I let it hit the bed, the servo's skip when it hits the bed and then it moves to the next test point. It never raises up to go to the next point.

I am running 1.21RC1, but have tried 1.20 and 1.19, same result with each. I'd greatly appreciate any hints or thoughts.

Thanks in advance.