[en] In the 3-50BT line connecting the two synchrotrons of the J-PARC, electromagnets for bending, quadrupole and steering are installed. The coils of these electromagnets are made of hollow conductors and adopt a direct cooling system in which cooling water passes through the conductors. In the period from March to April 2019, a layer short was caused due to water leakage in the coil of the B15D bending electromagnet, and eventually the beam could not be transported to the downstream synchrotron. After detecting the first failure, various investigations and first aid measures were performed on the B15D. We will introduce the inferences about possible changes in water leakage and layer shorting that have occurred within the coil that are considered from there. (author)