As for the PTT buttons, I think it's beyond incredible, that Boeing still has these silly rocker switches on the yoke! They are a recipe for totally unnecessary additional workload (as you unfortunately see in this case), additional confusion and a loss of situational awareness between pilots and ATC. No, I'm definitely NOT blaming the crew, but add weather, low fuel and wind shear to that, and the recipe for disaster is complete! Completely insane that aircraft can be certified like that, only to save $10 on some wires and a decent switch! The Airbus system (a toggle switch that can be firmly locked in intercom position) located on the central pedestal on the radio panel, whilst still having a PTT switch on the Side Stick, is a much better thought-out solution IMO.
Its entirely possible to have a 737 with a latching intercom system on the centre pedestal. All the ones belonging to Europes largest 737 operator have them anyway and I'm surprised that Transavia don't!