I have a pair of uniden walkie talkies that i use quite often and i recently braught some listen only earpieces they are 2.5mm which fit bt they do not work when i plug in the earpiece it transmits and dont stop until i take them out
the 2.5mm plug has different 'bands' on them. One of the metal bands, not the black plastic ones, is meant for the voice. as your earpieces do not have a voice side, they will be making contact, and the radios are thinking you are holding down the talk button. Which obviously does not exist.