[oscmejia08]

thanks @hfjbuis. Tested lowered acceleration and makes no difference. I also double checked hardware and I'm pretty sure that's not the issue.

I contacted StepperOnline since I'm using their nema 34 steppers and driver. They suggested I ran a test with an Arduino board, so I did.
I connected 2 pins and ground from an Arduino Uno to the driver, for the X axis.
I tested the same distance with different speeds and I always got the same travel.
I then reconnected the teensy and ran the same test using UGS, and:
1) If i send a command for the same distance with the same feed rate, it always travels exactly the same
2) If I change the feedrate for the same distance, actual travel changes
3) Even at a very low acceleration, If I change the feedrate, the actual travel is not the same.

This video shows my test: https://youtu.be/-V0ec9jldtY

Also attached is the Arduino code that I used in my test.

So, looks like the issue is Universal Gcode Sender? I can't find what could be wrong in the configuration, looks, simple.
Any ideas will be appreciated, I'm running out of them at this point.

[hfjbuis]

The arduino code sends a symmetrical pulse, all cnc controllers send a pulse that is 1..10 usec active. You could change the active high time to 10 usec and double the active low time. I should not make any difference but who knows. If it makes a difference, it is the driver, wiring or the step pin voltage or max current.

After you changed the controller and the gcode sender, you have a problem. That could be caused by UGS or by the Teensy. Both have a reputation of being reliable.

You could use the arduino serial connector to send the gcode to the Teensy. That should/could rule out UGS or the Teensy.

Please post your gcode so I can have a look at it to rule out the gcode.
How is the teensy connected to the driver?