Benbox Laser Machines/CO2 Lasers/3D Printers

Not if it was very marginal. I agree the the most likely related to the power supply but the laser is only 500mw. Perhaps a test might be to disengage the drive mechanism.

It got rid of the the nick in the circle at 10 o'clock!! I suspect the wave in the straight lines is due to wiggle in the laser mount carriage. I have it on my A3 fixture that has the carriage suspended on wheels (probably your configuration) and not on the core-xy fixture where the laser carriage is on linear bearings. Use the laser for etchings with lots of curves. Try the attached image. It is 0.1 mm resolution. On my 2.5W fixture I use speed 1200, power 255 for a dark burn on wood. 1500 might show the lines better

 I am 99.99& linux based and use a home brew application. It is a work in process but I have etched well over 500 slates, mirrors, and wood panels with it. No users guide or help. Attached 64-bit executable was built on Linux Fedora 27. It isn't as polished as T2 or BCL but works for me. If you try it, please prove feedback, positive or negative.

The latest set of A4988 drivers all came with the voltage at at 0.5V. I like to use 0.5 for the X and 0.8 for the Y. It runs the motors a little warmer than necessary.

As Zax said there are lots of tutorials online for current adjustment. I think the "best" is at polulo.com.

Attached is a picture of my favorite test pattern etched on 0.2mm cardstock. I live in a country without nice units so it took a while to find out what 160 GSM is!!!. It was etched on my most imprecise machine, a 2.5W A3 with sloppy wheels. It does have limit switches but they were used only on startup.
Lower image is one pass at 1200mm/min with power 100 out of 255. Upper image is four passes at 1200mm/min power 50. The straight lines are not great but completely repeatable. Also attached the gcode file. After I did the homing cycle I used the simple GrblController utility for the burns.

BTW - I built a core-xy with the linear rails and it is super smooth and precise.

Blame it on the diode gremlins! They get their nasty teeth into a wire and cause the electrons to flow in the wrong direction. They can sense when you are getting close to uncovering their den and then they go dormant. Just long enough to make you think you solved the problem. Sure cure is to get a 200W laser and zap their hangouts. Alternatively, purchase an upgrade replacement unit and they will migrate to it. BTW - the chief Electron Gremlin resides in my basement. Sometimes he takes a vacation via email or forum posts.

It might be advisable for you to start with simple shapes (square, circle, triangle) in plain gcode.  Manually locate the laser somewhere in the middle of the bed and etch with low power into Neon colored cardstock (cheap end reacts with low power). Once this is working as expected move on to more complex but well tested images. Then migrate to your final work flow.

You seems to have the startup woes experienced by almost every user on this forum. We expected to take our project and the tool would do everything perfectly by magic. I bought my first machine based on an online video. Lies, deception, and fraud. Put laser on shelf for a couple months assuming that it was a really poor decision. Found this group and now have 4 diode etchers and a K40 for cutting.

Try etching the attached sugar skull. It is 100x100mm (4x4inch) at 0.1mm resolution. With 2.5W laser I set speed at 1200mm/min and full power(255).

There is a simple grbl utility for positioning the X/Y/Z axis and interpreting user supplied gcode.

BTW - grbl has some user settable parameters for direction.

The supplied file "Scott outline small.svg" renders as 15 circles on my Linux system. When I examine the file there are entries for text. Wonder if you have a newer svg or Inkscape version.