Thanks for your feedback. Yes, splines are not supported in EasyGerb. One suggestion to eliminate splines is to save the DWG as an "AutoCAD 12 format" and then reload that DWG back into AutoCAD for EasyGerb conversion (Why? AutoCAD 12 DWG is a very old version of DWG that didn't yet support splines, so AutoCAD automatically converts the splines to polylines).
Note: We do have an external tool called "ACE Translator 3000" which can import any DWG file (with splines) and convert them to Gerber - it has the exact same options as EasyGerb. You just start EasyGerb, select DWG for the Import format, and Gerber for the Export format. If you're interested in ACE, here's more information: https://www.numericalinnovations.com/collections/ace-translator-3000