Modem problem with Xenix 2.3.3

[Donald H Madsen]

I am using Xenix386 2.3.3 and VP/ix 1.2 and after much searching have
discovered that at random times DCD goes slowly low and makes it
impossible to continue communication.  This happens when using C-Kermit
and while using the DOS program Mirror III.  It only happens infrequently,
but when transferring long files it does happen.  

It is frustrating after most of a long file has transferred to have it
stop.  If an attempt to leave the DOS communication program is made, it
hangs the terminal before completing the exit of VP/ix and the system
must be rebooted.

It seems likely that the problem is withing the serial driver.  It happens
whether I use the com1 port directly or when I use one of the 8 ports or
a non-intelligent version of a DigiBoard (PC/8).

The symtoms include line 8 (DCD) suddenly going low and line 20 RTS staying
high.  It happens with a 2400 Baud modem and with a 9600 Baud modem.

Any suggestions will be most appreciated.