co bug with multiple locks in RCS Version 5.7

[Packer, Vincent (Ex AS01)]

The development environment I am using has RCS version 5.7 running on
Slackware 9.0. A number of batch files and csh scripts are used to customise
RCS and make it available from Windows 2000 machines. Although the steps to
reproduce below may not be sensible in this context, they are in the case of
the environment I am using. I have reproduced the problem using the co
executable directly, so the problem is definitely not in the scripts.

Steps to reproduce:

Create a file test.txt with some contents.
ci -r780.1 -t-"Some description" -m"780 version" test.txt
co -l test.txt
modify test.txt
ci -r790.1 -m"790 version" test.txt
co -l test.txt
modify test.txt
ci -r800.1 -m"800 version" test.txt
co -l 780 test.txt
co -l 790 test.txt
co -l 800 test.txt

The last checkout appears to be successful but does not actually add another
lock to the file. The output of this command is attached in coout.txt. The
suspicious line in this is:
co: test.txt,v: multiple revisions locked by vcp; please specify one

The same output message is seen when trying to unlock one of two locks on
the same file and the unlock is unsuccessful. Attached is the RCS file
produced by the above commands.

 <<test.txt,v>>  <<coout.txt>> 

Regards,
Vincent Packer

test.txt,v
Description: Binary data

coout.txt
Description: Text document