This article reports on an investigation of students learning of physics during group discussions around context-rich problems in introductory physics courses at university level. We present the results from video recordings of student groups solving three different problems. We found that group discussions around physics problems can lead to stimulating and learning discussions of physics but we also observed situations when the discussions did not work well. Misunderstandings of physics concepts reported in the literature emerge in the discussions now and then but the students also detect new "problems". In the discussions most misunderstandings and problems are treated and solved either by the students themselves or by the students together with the teacher. Factors that stimulate a good discussion are engaging problems and a teacher at hand to answer questions and to discuss with the students. Factors that prevent a fruitful discussion are too little knowledge of the actual physics among the students and bad functioning of the groups.