A recent patch made it so equipping a heavy carrier means you can only carry two rockets/GL round in reserve. Unfortunately when you spawn/resupply, you only have one GL round/rocket in reserve, like you equipped a light carrier. You have to go to a supply box and equip your rocket launcher/GL and tap F to get your second rocket/GL round. I have only seen this happen on Checkpoint.
BUG: Demolitions class missing a Rocket/GL round upon spawn/resupply