Does drinking yeast beer (known in Germany als Hefe-Weissbier) have any potential influence on gastric problems?
Yeast can become active in intestines, starting there fermentation processes and causing bloating. When such symptoms occur, is that the effect of yeast activity, or it's rather some kind of food intolerance?
In a nut shell, a definite answer is not always easy to come by in medicine since many factors can give different results. Anything from the make up of your intestinal flora, your diet, to medications you take can have different affects that may be causing bloating or excessive flatulance. To answer your question, yes it could be the yeast activity but also it may be an intolerance to the yeast itself, also the bacteria in your intestines may not like the "new" yeast introduced and may produce additional toxins. Or a combination of all this plus more.
Our bodies are ecosystems as much as they are machines. We have a wide variety of microbes in our intestines and even if the yeast is not the culprit something else could be encouraged to grow. I tend to suspect this is the real problem for the entirely unscientific reason that I have never noticed pasteurization to affect whether I am bloated after drinking beer (and sometimes it happens, and sometimes it doesn't).
So in answer to your question, it is complicated, and it might be a factor but it is almost certainly not the only one.