Using the ET_2015_11 release, Carpet incorrectly replaces sets of components with their containing bbox, leading to a large increase in the number of grid points on the corresponding refinement level. This reduces simulation speed and causes increased memory usage (a lot). Using the same parameter file, this problem is visible with ET_2015_11, but not with ET_2014_05. Setting CARPET_DISABLE_BBOXSET2, or setting CarpetRegrid2::min_fraction = 1, both work around the problem. The bboxset2 code was enabled between these two releases, so this points to a problem with the code in bboxset2 that is used to determine whether to use the containing box or not. I attach parameter files and grid structure visualisations which demonstrate the problem. The parameters files differ only in the use of min_fraction = 1, but the same change is observed if you compile with -DCARPET_DISABLE_BBOXSET2 in CPPFLAGS.