There seems to be an "attractiveness" to different buildings (or attractions, rides, etc) that may be causing the guests to ignore their own hunger and go to these places. It also happens with some animals. It can also cause overcrowding of guests to these animals or buildings. I find if you put in a highly attractive animal (Panda) or ride (the tiger show seems to do this) you get a large flock of guests in that area until they have had a chance to view it. This can also cause some guests to drop their happiness level due to the overcrowding, or hunger needs. Sometimes you just gotta ride it out!
With some user created animals, the attractivness is set to 100 - which may cause a guest flow imbalance. Using APE I reset them to the range used in the game for similar animals (5 to 50-ish).
Also, check your guests' thoughts as they pass by the restaurant. Some may say "restaurant blah blah is too crowded". There is also a capacity for various buildings. The Lumberjack restaurant won't hold very many compared to the in game one, while the Zoo *** Lodge moves lots of em in and out.
If you have just a few out of a thousand, I wouldn't worry about it.