In this paper the potting failures of inserts in sandwich structure is analyzed. The case of inserts potted with syntactic foam is investigated. First, a discussion about the influence of defects is made. Then, an experimental campaign is performed to determine the traction and compression behavior of the syntactic foam. Later, a specific technological pull-out test was performed, while a DIC system was used to record the tests. This allowed to observe and understand the different potting failure modes of inserts for sandwich panels. The obtained results suggest that the potting failure of inserts is predominant when fabrication or installation defects are present.