Bulimic me?

My M thinks that there's a mystery going on. And it's gotta do with my dinners and tummy.

Strangely for the past few weeks, whenever I eat at Grand M's home (my GrandM cooks my dinner when I go over with my baby sister), I will regurgitate a portion of my dinner. Sometimes it's almost immediate, like 5 minutes after dinner. Sometimes I wait til we're on the way home before puking downstairs.

However, I can keep my dinner in my tummy when I eat at my own home. And the other day I had dinner at my Grand MM's home and I didn't puke too.

So my M wondered why do I only puke at my Grand M's home when I'm being fed the same food. The only difference is the cooking method. She thinks that GrandM adds too much water when boiling my meat so I end up with a very soupy dinner and that's what caused the puking. But GrandM argued that my big brother Herbie used to eat the same thing without any problems. She even made sure the meat was thoroughly cooked to kill all 'germs'. I guess my M didn't tell her sometimes I get raw meat, so uncooked meat is perfectly fine with me.

So now my M is testing to see if it's really the different cooking methods. She cooked my dinner personally at GrandM's house last night and I didn't puke. So she'll be trying it a few more times to see if the change in the cooking method helps.

Does anyone have any idea why I only puke at my GrandM's place? Maybe it's the fengshui?