Does anyone here have experience with symptoms of both gastroparesis and dumping syndrome?

Over the past many years I've seemed to go back and forth between them. I can eat a meal and it will sit in my stomach for 10+ hours causing extreme bloating, nausea, fullness, etc. and then if I manage to eat again it can have the exact opposite symptoms: stomach emptying almost immediately with cramping and diarrhea with burning acid pain as all my stomach acid gets dumped too.

I've tried probiotics, digestive enzymes, cutting out dairy and gluten, and more recently I've been trying the SCD diet. Nothing seems to work or help. I don't know of anything that could have caused this; no Antibiotic use to speak of, no known vagus nerve damage or surgery in that area, no diabetes or other health problems before this started. I've had loads of tests with no clear diagnosis or problem found.

Anyone with a similar experience or any ideas? Thanks.