Breakout board trigger voltage level


We are using CW506 Breakout board to attack 5V target with the CW-lite and we’ve noticed that the voltage level on the trigger pin on the CW side is 2.3V instead of 3.3V (the pin is TIO4 on the board). The rest of the signals are fine: Rx and Tx have 3.3V. Is this a board malfunction or is there are a reason that a trigger should have a lower level?
Many thanks in advance.