CVS merging

[CRISP Norman]

Question regarding merging.

In the diagram below the version numbers represent changes made to one
particular file as time moves forward.
What has happened is that the after the last merge back from the feature
dev branch to the staging branch the contents of 1.2.14.3 has the
content of 1.2.18.1, completely ignoring the update that was made to
1.2.14.2.  I would have expected a conflict to occur as both revisions
(1.2.14.2 and 1.2.18.1) as both updates only one change on the exact
same line.

I don't normally pay any attention to revision numbers as we do rely on
tags, but for this example the revision numbers were easier to explain.

Command used to update is something like:
Cvs update -kk -P -d -j TAG_OF_LAST_MERGE -j CURRENT_BRANCH_TAG filename

Does anyone know why 1.2.14.2 was ignored at merge time?

1.2.14.1 = 1.2.18.1
1.2.14.2 = update in staging branch
1.2.14.3 = result of merge from development branch to stage branch
Now 1.2.14.1 = 1.2.18.1 = 1.2.14.3


Thanks
Norm.

               1.2
MAIN TRUNK
------------------------------------------------------------------------
-----
                |
                |      1.2.14.1    1.2.14.2           1.2.14.3
STAGING BRANCH
--------x-----------x-------------------x-------------------------------
-
                     |         |                       |
                     |         |1.2.18.1               |
Feature Dev Branch
------------x--------------------------------------------------------
                  creation     merge stage to dev     merge back to
staging