Random Letters Missing During Laser Cut – Only Works Fine One Letter at a Time

For a Ruida controller, this is almost certainly due to a communication problem causing a loss of commands & data between the Mac and the controller.

If the machine is connected to the Mac through a USB cable, then this is definitely a communication problem.

Although you can try a known-good / high quality USB cable, using the controller’s Ethernet connection is generally the best way out. The doc covers the basics:

This discussion of a similar problem has some details: