Opportunities for programming education have been increasing, and enrichment of guidance is needed. To provide precise guidance in programming exercises, instructors need to successfully grasp learners' impasses. However, this is difficult in exercises at universities since few instructors need to deal with many learners. In this research, we focus on the characteristic traces left by a learner repeatedly writing and erasing source code in a program (exploratory traces). Our goal is to develop methods for automatically estimating students stumbling in construction of program logic on the basis of the analysis of exploratory traces. This paper mainly describes the methods for analyzing exploratory traces along with examples. We also describe experiments applying our methods to actual programming and discuss their effectiveness on the basis of their results.