Win 95 not releasing Com port to DOS app

Running Win 95 on 60 Compaq Deskpro EN 815e’s with external US Robotics Modems with a Must use DOS EDI software. Software loades and runs fine up to dialing at which point it frezes up. Modems Work fine with Windows apps, and DOS EDI can transmit fine if we shut down and restart in DOS. Looking for a fix so we can at least run it in DOS window with out reboot.