It was I can tell you, it happened on pushback as well which didn't help. Swopped boxes around etc etc checked ant and cabling for moisture etc. I think it was more by luck than anything else in the end after much head scratching and 'expert' advice. I remembered from something similar from many moons previous and it worked. Got told off by QA a week later because I should of had a dispensation to fly with no transceiver installed although you can go with 1 vhf inop under the mel, still with 300+ pax grateful it was worth it.