thank you for the information furnished, now it is enough for me to see the problem.
the other webserver, when receiving a request withouth the trailing slash does not fullfil the request but answer with a redirection to the version with the slash.
the real problem in HFS is that it serves the request immediately without first redirecting the client. indeed, it is the client that forms URLs, and it forms wrong URLs if the slash is missing.
the best thing to do, AFAISee, is to behave the same way the other server do.
i will add this fix to the to-do list.