There’s a problem with the stroke data for 添 that leaves the last four strokes uncolored.
Looking at the other mnemonics leads me to believe that originally indebted忝 was not one of the parts provided, so most people used calamity夭 and heart ⺗ or filled in the strokes manually. Now 忝 is present in the parts list, so manual filling is no longer an option, but 忝 seems to have the same strokes as 夭.