Fails to remove title from video

[randomparity]

When I run the command below, the script correctly identifies the file as having a title and runs mkvmerge to remove the title. After the script has completed, if I view the mkv file with VLC it still shows a title. If I run the same script again, it still sees a title and runs again, and again fails to remove the title.

Running the script on Debian 9 (Stretch).

----- script command line ----
python2 ~/Movies/scripts/videoslimmer/VideoSlimmer.py --mkvmerge /usr/bin/mkvmerge --media ~/Movies/library/hd/Hard\ to\ Kill\ (1990) --lang eng --delete-title yes --loglevel debug --logpath ~/Movies/scripts/videoslimmer/logs

----- videoslimmer.log -----
2019-04-06 11:01:00,693 INFO VideoSlimmer videoslimmer :: [BEGIN] VideoSlimmer processing started
2019-04-06 11:01:00,711 DEBUG VideoSlimmer videoslimmer :: filename without extension is "Hard to Kill (1990) - [REMUX-1080P][DTS-HD MA 5.1][H264]"
2019-04-06 11:01:00,711 INFO VideoSlimmer videoslimmer :: Processing file /home/sysadmin/Movies/library/hd/Hard to Kill (1990)/Hard to Kill (1990) - [REMUX-1080P][DTS-HD MA 5.1][H264].mkv
2019-04-06 11:01:00,711 DEBUG VideoSlimmer videoslimmer :: analysing file "Hard to Kill (1990) - [REMUX-1080P][DTS-HD MA 5.1][H264].mkv"
2019-04-06 11:01:00,711 DEBUG VideoSlimmer videoslimmer :: path to file is "/home/sysadmin/Movies/library/hd/Hard to Kill (1990)"
2019-04-06 11:01:00,711 DEBUG VideoSlimmer videoslimmer :: mkvmerge command to query file is "[u'/usr/bin/mkvmerge', u'--identify-verbose', u'/home/sysadmin/Movies/library/hd/Hard to Kill (1990)/Hard to Kill (1990) - [REMUX-1080P][DTS-HD MA 5.1][H264].mkv']"
2019-04-06 11:01:00,806 INFO VideoSlimmer audio_tracks :: no audio tracks to remove
2019-04-06 11:01:00,806 INFO VideoSlimmer subtitle_tracks :: no subtitles to remove
2019-04-06 11:01:00,806 INFO VideoSlimmer edit_metadata_title :: metadata title is not blank, marking for rewrite...
2019-04-06 11:01:00,806 DEBUG VideoSlimmer videoslimmer :: mkvmerge command to edit file is "[u'/usr/bin/mkvmerge', u'-o', u'/home/sysadmin/Movies/library/hd/Hard to Kill (1990)/Hard to Kill (1990) - [REMUX-1080P][DTS-HD MA 5.1][H264].mkv.temp', u'--title', u'', u'/home/sysadmin/Movies/library/hd/Hard to Kill (1990)/Hard to Kill (1990) - [REMUX-1080P][DTS-HD MA 5.1][H264].mkv']"
2019-04-06 11:03:15,380 DEBUG VideoSlimmer videoslimmer :: mkvmerge returned success
2019-04-06 11:03:15,531 DEBUG VideoSlimmer videoslimmer :: removed source file "/home/sysadmin/Movies/library/hd/Hard to Kill (1990)/Hard to Kill (1990) - [REMUX-1080P][DTS-HD MA 5.1][H264].mkv"
2019-04-06 11:03:15,532 DEBUG VideoSlimmer videoslimmer :: renamed temporary file from "Hard to Kill (1990) - [REMUX-1080P][DTS-HD MA 5.1][H264].mkv.temp" to "Hard to Kill (1990) - [REMUX-1080P][DTS-HD MA 5.1][H264].mkv"
2019-04-06 11:03:15,532 INFO VideoSlimmer videoslimmer :: [SUCCESS] Processing finished
2019-04-06 11:03:15,532 INFO VideoSlimmer videoslimmer :: [EXIT] VideoSlimmer finished

----- mkvmerge -----
mkvmerge v9.8.0 ('Kuglblids') 64bit