Bad segmentation - missing </mrk> tag in the target XLIFF file

Hello,

I have a problem regarding the marker element </mrk> a of a target *.xlf file. Sometimes, a target translation of a segment is not enclosed correctly by </mrk> tag, but reamins unclosed with the opening tag in this form: <mrk mtype="seg" mid="[number-of-segment]" />.  This problem seems to affect the segments randomly: target files, results of work of different translators who worked with the same source file, do not follow any pattern in distribution of this problem. See the example below:

This is a source

            <trans-unit id="834" datatype="plaintext" resname="apm_AlertMessages.DaemonNotRunning" extradata="First batch">
                <source>APM has stopped.</source>
                <seg-source>
                    <mrk mtype="seg" mid="1">APM has stopped.</mrk>
                </seg-source>
                <target>
                    <mrk mtype="seg" mid="1"/>
                </target>
                <note/>
            </trans-unit>
 
This is a target translation in Spanish. Note the correct presence of </mrk> tag in <target>:
 
            <trans-unit id="834" datatype="plaintext" resname="apm_AlertMessages.DaemonNotRunning" extradata="First batch">
                <source>APM has stopped.</source>
                <seg-source>
                    <mrk mtype="seg" mid="1">APM has stopped.</mrk>
                </seg-source>
                <target state="final">
                    <mrk mtype="seg" mid="1">Se ha detenido APM.</mrk>
                </target>
                <note />
            </trans-unit>
 
And this is a target of the same source, now in French. Here, the </mrk> is missing:
 
            <trans-unit id="834" datatype="plaintext" resname="apm_AlertMessages.DaemonNotRunning" extradata="First batch">
                <source>APM has stopped.</source>
                <seg-source>
                    <mrk mtype="seg" mid="1">APM has stopped.</mrk>
                </seg-source>
                <target state="final">
                    <mrk mtype="seg" mid="1" />APM s'est arrêté.
                </target>
                <note />
            </trans-unit>
 
I'd like to know how to adjust the source file to make it work properly - this way the targets do not show up at all in SDL Trados. It doesn't seem to be a problem of the source file though, because some targets can cope with the above-mentioned form of empty target translation (<mrk mtype="seg" mid="[number-of-segment]" />) just fine. The translators use SDL Trados 2011.
 
Does anyone have any idea? I'd be grateful for any comments and suggestions.
 
Thank you!
 
Best Regards,
Jonáš.