We recently proposed a new frustration mechanism that occurs in a space-time crystal, i.e. a media which properties are varied both in space and time. The latter consists in a chain of pendulums parametrically excited by a propagating wave. In such chain, a phase dislocation must appear somewhere due to topological constrains. We have studied the dynamic of a single dislocation in great details, and show that the propagation of the dislocation ensures the ergodicity of the system. However, there can also be a larger (but odd) number of dislocations, which collective behaviour remains to understand. Hence, the goal of the internship is to probe theoretically, numerically and experimentally the interactions between several defects. Particular attention will be given to the creation/anihilation of pairs of defects. Depending on the candidate interest, other questions such as 2D generalization, link with topological insulators or synchronization processes may be explored. This project may find applications for analog computing in Ising machines.