Unfortunately, even if these weren't pictures for ants, it wouldn't be worth enough words to come up with a solution, other than the fact that it's obvious that these are not the default appearances of these events, so it's caused by some kind of script you're using.
It's possible that the offending character can be captured in the clipboard, but not guaranteed.
1. Paste this next command into any editbox, but don't yet press ENTER, because we still need the clipboard from the next step.
//bset -t &v 1 $cb | echo -a $bvar(&v,1-)
2. Highlight the line with your left mouse button, then let go of the button when a range including the square is highlighted. This puts the range into your clipboard without needing to press Control+C. Since this is a visible character, you probably do not need to hold down the CONTROL button to include the color codes, so try it first without pressing CONTROL at the time you let go of the mouse button.
3. Now press ENTER to execute the command from #1. This should show the byte values for everything in the 1st line of your clipboard. The numbers 0-255 are the $asc(char) numbers for each byte in the clipboard, and it's possible that some characters are UTF-8 encoded into multiple byte values.
The numbers 0 thru 9 have $asc() values 48 thru 57, so hopefully those can help you locate which strange character is causing this.