Thank you Brian for your quick answer, I have tested your suggestions.
Also the scan was not successful, everything is clean.

I should add, that this failed import and the conversion of *. DXF to *. 0G in the "CAVACAD" also occurs without DOSBOX in newer operating systems like Windows 2000 and Windows XP. Only the old PC from 1997 with the old DOS and Windows 3.11 does not cause any problems. I suspect that since the 32 BIT systems a Microsoft addition has been added, which is not 100% compatible with the old "CAVACAD". But what?

It's a pity that all of the Italian software developers seem to be retired. Or just want to sell only more new systems...? (TPA Milano).
Because they prefer not to give any information about the old systems.

Best Regards
Franz