Not a pump user, but just a random thought, I had a bit of lipohypertrophy going at the sides of my stomach which affects absorption, so moved to my stomach to let the lipo break down. Is there a soft fleshy mass like a bit of avocado under the cannula site? The high followed by the plummet to 49 kinda sounds like an absorption problem, lots of insulin inhibited from absorbing, then releases in one go.
Could be a hundred and one other things, I'm sure some pumpers will be along soon.