My longer B1 30 watt has been working great for 3 months of heavy use. I was going to cut one last thing before quitting today. BUT the engraving was to long. I did some testing and cut some 2x2 inch squares. They were all 2” wide but 2 1/4” long. Tried a 2” by 4” and had the correct 2 width but was about 4 9/16” long.It seems the longer the dimension for more it is off. I have no idea where to look for this problem. Let me know what info you might need to help. This is with a GTBL - Longer B! 20W 30W 40W profile provided by Longer. UPDATE if I switch to just the GTBL profile it cuts the correct sizes.
Look at GRBL parameters $100 and $101. Typical values are 40, 80, and 100. What you are looking for is that they are equal.
Any chance you made a parameters backup sometime in the past?
Thanks for the reply. I am very new to Grbl and don’t know where to look or how to change these.
Dave
Make sure you have not (inadvertently) enabled Rotary Mode:
Thanks, will go out now to the garage and check that. It is 19 degrees here right now.
Not in the Garage I hope!!! 
In the Console window, enter $$ and it will list all the GRBL parameters.
Change nothing without knowing what it does, why you are changing it, and what the expected result will be. Always make a backup copy before changing anything. You can copy them from the Console window and paste to a text file.
Thanks, that was the problem. I now remember reading about the rotary mode causing problems since it was so easy to accidentally
Thanks for the info. I do have a small electric heater that keeps it at around 60 degrees when it is this cold. I have a My Buddy heater that I only turn when I am in the garage and have my ventilation system going with a very small crack of the garage door being open (no windows). Also have air and CO monitors going.
Thank you very much