Hi there. I as well had the same surgery a few years ago. Over time I have had the same sudden pain, sometimes bringing me to the er with all labs in normal range.
My theory is that diverticulosis sometimes goes hand in hand with what is called irritable bowel, a diagnosis of unknown painful and irregularity of the bowel.
Medically speaking, post operatively there can be adhesions which can tug and twist the bowel, causing sudden pain. Gas, too much fiber, diet, food intolerance can cause disrupts in motility as well as nerves and anxiousness, which can effect the bowel too. Through trial and error I found what foods agree and don’t with me. I also eat a healthy diet.
Experimenting with food and fiber might help. Gas and constipation can cause severe pain too. I’ve gotten spasms which were relieved with muscle relaxers.
If it continues, you need to speak with gi. There are tests to make sure what goes in flows well.
After my surgery I did notice my motility slowed a bit due to nerves being effected by surgery.
Stew fruit to make it easier to digest. Cook veggies and avoid gassy ones. Milk is gassy. I drink grass fed organic milk, meat, yogurt, all in small amounts. Try aged cheese. I do well with a bit every day. Get your gut into prime shape with good food.
A nutritionist/ dietician, or physician specializing in this area is helpful. They can test for food intolerance.
See doctor if persists, and don’t be afraid to change if you don’t get answers.
Hope I helped a little.