Event toggleBrushesFlyout returns unrecognized value

When I subscribe to 'toggleBrushesFlyout' whenever I enter or leave the said window (adjusting the brush radius/hardness for example) the event triggers but it gives me different event results:

  à

or

  W

or

  ?

I tried to force it to convert the received bytes into a UTF-8 string but that also does not seem to make a difference. I also cannot find anything related in the scripting guide. All other events I am using just return the proper (readable) char ids or string ids, but this one seems to be different.
What is it returning me and how can I handle it properly?