Motion exceeds time limit - by a lot!

[lucmp]

I had an unpleasant surprise with motion today.

I leave motion running continuously and configured to detect movement within certain constraints, and to record and upload a few seconds around those detected moments.

Mind you, the camera captures a little bit of street movement and that has been OK for many days because my configuration filters out most of the noise movement. I swear, it has been working just fine for days. Motion has been uploading about 20MB of footage to my remote server every day. This is exactly what I want. I don't want to use a mask for strategic reasons. I want street movement to be detected provided it is within the preset limits. Like I said, this arrangement has been working very well for days.

Here is part of my configuration that I believe to be relevant:

emulate_motion off
threshold 12000
noise_level 32
minimum_motion_frames 20
event_gap 1
pre_capture 2
post_capture 6
movie_output on
movie_max_time 30
movie_quality 100
movie_codec flv
movie_passthrough on

Today, after leaving motion running for the night and the entire day, I came back to find out that motion had uploaded 1.3GB of footage! That is bad because I have a monthly quota with my Internet provider.

Upon inspection, I found that motion had recorded and uploaded many movies as long as 30 minutes! Some are shorter, like 15 or 23 minutes, but most are exactly 30 minutes plus a few random seconds.

The comment in the configuration file indicates that movie_max_time is measured in seconds, not minutes.

# Maximum length of movie in seconds.
movie_max_time 30

So does the online manual
https://motion-project.github.io/motion_config.html#movie_max_time

My configuration limits movies to 30 seconds. Why is motion not respecting the limit?