While working on 2m band and high power, when the microphone is held too close to the antenna, the PTT 'hangs' in TX mode when going over to RX and/or there is sometimes no modulation during TX.
This is due to RFI on the PTT line going into the display/controller unit, and can be particularly annoying when working mobile with an antenna affixed to the front windshield (like PROCOM 'Glassfix' dualbander).
RFI can be drastically reduced by inserting a 10 to 22nF capacitor between PTT line and ground (scratch a little bit of the PCB varnish), on the RJ-45 plug in the controller unit. See picture. If SMD capacitor not available, then try with a chip capacitor, solder the 'ground' side on big solder pad (solder of the potentiometer casing).