Creating a logger_topics.txt file breaks logging

I have created a new topic for my drone.
It works well, I manage to publish from one module and subscribe to it from another.

I’d like to have its values on my log files, so I create a file called logger_topics.txt inside of the microsd card at /etc/logging, just as explained here:

The only contents of this file are:

test_motors_state 30

Since test_motors_state is the name of the topic and 30 is the frequency I want it to be logged.

Sadly though, when I analyze the generated ulog file with flight review, it plots absolutely nothing.
I also tried to write only test_motors_state without a frequency parameter, same thing happens.

And then everything starts working again when I delete this file.

Does anyone have any idea what might be causing it? Thanks!