I have observed the issue shared by you and request you to please first try using latest Aspose.CAD 18.8 on your end. If there is still an issue then please share the source file and used sample code to reproduce the issue on our end.
I have worked with file shared by you using Aspose.CAD for .NET 18.8 and have been able to observe the issue. A ticket with ID CADNET-685 has been created in our issue tracking system to further investigate and resolve the issue. This thread has been linked with issue so that you may be automatically notified once issue will be fixed.