Illustrater files corrupting in EZCAD

Hi community.

I hope some one can help. I have created some very detailed illustrater designs, and sent them to be  laser engraved. When the engraver opens my illustrations in the EZCAD softwear, curved areas have become straight. Some areas of the design have straight lines across them instead of following the curved line of my drawing. The designes were hand drawn with a pen and tablet using the paint brush tool on illustrator, Out line strokes was selected with a colour but there was no infill colour selected as the designes were made up of lines and dots. They are verry intricate and detailed, but one colour.

I followed advice on youtube in how to export them for engravibg. I.e- I exbanded the design, merged it, chose one colour and then united all the colours as one. This worked well and I was able to send the designs with no white back ground, just the lines.  But as I said, when these designes are opened in EZCAD softwear the curved line is becoming anguar and straight. Any body got any idea on what could be going wrong. I am new to this process and illustrator so maybe I have made a mistake in how I drew it.  Any thoughts?