In the HSC detectors, charge can pool at the top/bottom of the device. The level (~ 20k) is significantly under the saturation level, so it doesn't get masked and there's no simple way to identify it. Without ignoring EDGE pixels during coaddition (removed in
DM-9953), these bad pixels leak into the coadds. We need to revert commit 5faadffd2f408b019280ea1c353f0ec787b092b9.