We have been fairly badly affected by autofs bugs:
#55931 and #65003 in bugzilla.  I have already
attached comments and a suggested workaround to these
bugs; would appreciate feedback and ideally a
new patched version of autofs, 
This is yet another related problem with autofs has 
just come to light which my
workaround is not able to address:

Context: autofs-3.1.7-21 and kernel-2.4.9-e.3
rpms from AS2.1.

automounts are looked up in NIS.  One such
mount is mounted and busy (files under it used
by running processes).  While still mounted,
the NIS maps are changed so that a new mount is
configured for that same mountpoint.

Problem: The next time requests are made for
that mountpoint, autofs will automount the new
mount over the old one.  As Alan Cox suggests in
bug #65003 above, autofs should *never* allow 
multiple mounts on the same point.

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Context: autofs-3.1.7-21 and kernel-2.4.9-e.3 rpms from AS2.1. 

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Stock ypbind-1.8-1 AS2.1.
There is nothing else installed which could interfere with
this behaviour.

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It happened without the patch from bug 65003, but the patch will not
fix the NIS bug, only the two other bugs, since the
patch only affects stopping and starting the autofs
service, whereas the NIS bug is the only bug of the 3
which occurs without doing a stop or a start (or a restart).

That is why my patch is more of a workaround - a proper
fix should probably go in daemon/automount.c in the
autofs source.