Hello and welcome to the forum!
Mo Mo may be eating too fast and regurgitating. Regurgitation is what it's called when the food comes right back up. It can be caused by eating too much too quickly, obstructions, hair balls, or gas to name a few things.
If it happens only once every three weeks my guess would be hair balls. Brushing Mo Mo daily, regular exercise and using a hair ball remedy periodically may help.
(when giving hair ball remedy, always give it on an empty stomach, and wait two hours before feeding. Start with once a week.)
If you are feeding kibble I would recommend you start adding some canned food to his diet.
And feed small portions 15 minutes apart instead of all at once.