Atoms in molecule not bound by any form of constraint

GROMACS version: 2019.6
GROMACS modification: No

I am running a coarse-grained simulation, and I am seeing the following note:
NOTE 4 [file topol.top, line 75]:
In moleculetype ‘PNM’ 40 atoms are not bound by a potential or constraint
to any other atom in the same moleculetype. Although technically this
might not cause issues in a simulation, this often means that the user
forgot to add a bond/potential/constraint or put multiple molecules in
the same moleculetype definition by mistake. Run with -v to get
information for each atom.

I don’t understand why I am seeing this note. I am running a custom linear polymer simulation with the terminal beads being a certain type (TTA, TTB), and every nonterminal bead is the same type.

This is my topol.top file:

#define _FF_GROMACS
#define _FF_GROMACS1

[ defaults ]
;nbfunc comb-rule   gen-pairs   fudgeLJ fudgeQQ
1   1   no  1.0 1.0

[ atomtypes ]
;type   mass    charge  ptype   sigma   epsilon
TTA 114 0.000   A   0.000   1.000
TTB 114 0.000   A   0.000   1.000
TM  113 0.000   A   0.000   1.000
TW  18.010  0.000   A   0.000   1.0000

[ moleculetype ]
;name   nrexcel
PNM 3

[ atoms ]
;   nr  atoms   resnr   residue atom    cgnr    charge  mass    typeB   chargeB massB
    1   TTA 1   PNM BTA 1   0.000
    2   TM  2   PNM BM2 2   0.000
    3   TM  3   PNM BM3 3   0.000
    4   TM  4   PNM BM4 4   0.000
    5   TM  5   PNM BM5 5   0.000
    6   TM  6   PNM BM6 6   0.000
    7   TM  7   PNM BM7 7   0.000
    8   TM  8   PNM BM8 8   0.000
    9   TM  9   PNM BM9 9   0.000
    10  TM  10  PNM BM10    10  0.000
    11  TM  11  PNM BM11    11  0.000
    12  TM  12  PNM BM12    12  0.000
    13  TM  13  PNM BM13    13  0.000
    14  TM  14  PNM BM14    14  0.000
    15  TM  15  PNM BM15    15  0.000
    16  TM  16  PNM BM16    16  0.000
    17  TM  17  PNM BM17    17  0.000
    18  TM  18  PNM BM18    18  0.000
    19  TM  19  PNM BM19    19  0.000
    20  TM  20  PNM BM20    20  0.000
    21  TM  21  PNM BM21    21  0.000
    22  TM  22  PNM BM22    22  0.000
    23  TM  23  PNM BM23    23  0.000
    24  TM  24  PNM BM24    24  0.000
    25  TM  25  PNM BM25    25  0.000
    26  TM  26  PNM BM26    26  0.000
    27  TM  27  PNM BM27    27  0.000
    28  TM  28  PNM BM28    28  0.000
    29  TM  29  PNM BM29    29  0.000
    30  TM  30  PNM BM30    30  0.000
    31  TM  31  PNM BM31    31  0.000
    32  TM  32  PNM BM32    32  0.000
    33  TM  33  PNM BM33    33  0.000
    34  TM  34  PNM BM34    34  0.000
    35  TM  35  PNM BM35    35  0.000
    36  TM  36  PNM BM36    36  0.000
    37  TM  37  PNM BM37    37  0.000
    38  TM  38  PNM BM38    38  0.000
    39  TM  39  PNM BM39    39  0.000
    40  TTB 40  PNM BTB 40  0.000

[ bonds ]
;
    1   2   1   0.5 100000
    2   3   1   0.5 100000
    3   4   1   0.5 100000
    4   5   1   0.5 100000
    5   6   1   0.5 100000
    6   7   1   0.5 100000
    7   8   1   0.5 100000
    8   9   1   0.5 100000
    9   10  1   0.5 100000
    10  11  1   0.5 100000
    11  12  1   0.5 100000
    12  13  1   0.5 100000
    13  14  1   0.5 100000
    14  15  1   0.5 100000
    15  16  1   0.5 100000
    16  17  1   0.5 100000
    17  18  1   0.5 100000
    18  19  1   0.5 100000
    19  20  1   0.5 100000
    20  21  1   0.5 100000
    21  22  1   0.5 100000
    22  23  1   0.5 100000
    23  24  1   0.5 100000
    24  25  1   0.5 100000
    25  26  1   0.5 100000
    26  27  1   0.5 100000
    27  28  1   0.5 100000
    28  29  1   0.5 100000
    29  30  1   0.5 100000
    30  31  1   0.5 100000
    31  32  1   0.5 100000
    32  33  1   0.5 100000
    33  34  1   0.5 100000
    34  35  1   0.5 100000
    35  36  1   0.5 100000
    36  37  1   0.5 100000
    37  38  1   0.5 100000
    38  39  1   0.5 100000
    39  40  1   0.5 100000

[ moleculetype ]
;
SOL 1
[ atoms ]
;
    1   TW  1   SOL BW  1   0.0000

[ system ]
40nipam-in-water

[ molecules ]
;compound # mol 
PNM 1
SOL 10994

I have provided bond constraints to my atoms, but apparently that does not suffice? Any advice would be appreciated.

Have you done this? What diagnostic information does it provide?