MIDI messages sent back to the controller are repeated

I wanted to send sysex messages back to my controller, but noticed the script sends the same message 11 times. I did a simple test creating a reaction that is triggered when one button is pressed. The action is just sending the following sysex message (there's not any loop or extra code before):

self._send_midi((240, 0, 0, 102, 16, 1))

I'm attaching what the controller is receiving in its input from the script. The button pressed is sent from the controller (CC 39, value 127), and the script sends back 11 sysex messages. I did also the test sending back a MIDI CC value instead of sysex (raw) messages and the same thing happens.

Is this a bug?