Maybe read both as different frames and if one is not complete drop the frame.
DTR C C C 0 1 N N N 25.913 0.577 29.346 -4.393 0.392 6.694 C DTR 13
DTR O O O 0 1 N N N 26.347 0.870 28.231 -5.360 0.640 7.407 O DTR 14
DTR OXT OXT O 0 1 N Y N ? ? ? -3.933 -0.869 6.514 OXT DTR 15
DTR H H H 0 1 N N N 25.005 -0.686 31.227 -4.431 3.093 7.035 H DTR 16
DTR HN2 HN2 H 0 1 N Y N 26.304 -1.341 31.969 -2.722 3.230 6.698 HN2 DTR 17
Need to backup to reading ideal coordinates in case model coordinates are not complete https://files.rcsb.org/ligands/view/DTR.cif
Maybe read both as different frames and if one is not complete drop the frame.