
I don't understand your feeding schedule - dinner time and tea time - oh wait, dinner = LUNCH? If this is going on, it could suggest an empty tummy so why not feed breakfast around 7 am and the second meal around 5 pm. That should make for a more even spread of food.
I occasionally got this with my hounds - middle of the night bile upchuck and my current one started doing this until I worked out that giving him a small amount of tinned Chappie just before he went to bed, around 10 pm, stopped all that. I did have to reduce the amount in his normal 2 meals or risk him putting on too much weight