pd.read_fwf behave different in python 3.9.7 compared to python 3.5.2

Question

I am a python rookie that used python code developed by a previous coworker. I have this file (life_time.txt) that needs to be read by the python script:

     1_3         1_4        1_10         1_5         1_6         2_3         2_8         3_4         3_9        4_10         5_6         5_9         5_8        6_10         7_8         8_9        9_10

 7066.30     4951.00   204664.31     2027.60    14498.40    41686.40     1077.00    21773.37    13321.70   284136.73     9401.60     5247.40     5802.00    67727.50   783031.81       24.00       66.00
 1768.93     2421.83    84863.77       70.04     2571.77    11872.19        2.11     3917.00     1692.92    87771.22     2227.40      914.76     1104.45    23971.41    61028.71        0.00        0.00

This piece of a python script (running V.3.5.2) does the job correctly (I added the prints to try to understand the problem):

filepath_t = path + '/life_time.txt'
t_raw = pd.read_fwf(filepath_t, header=0).values
print('Test')
print(pd.__version__)
print(t_raw)
t = (t_raw[0, :]).tolist()
print(t)
t_std = (t_raw[1, :]).tolist()
print(t_std)

This is the output:

Test
0.18.1
[[  7.06630000e+03   4.95100000e+03   2.04664310e+05   2.02760000e+03
    1.44984000e+04   4.16864000e+04   1.07700000e+03   2.17733700e+04
    1.33217000e+04   2.84136730e+05   9.40160000e+03   5.24740000e+03
    5.80200000e+03   6.77275000e+04   7.83031810e+05   2.40000000e+01
    6.60000000e+01]
 [  1.76893000e+03   2.42183000e+03   8.48637700e+04   7.00400000e+01
    2.57177000e+03   1.18721900e+04   2.11000000e+00   3.91700000e+03
    1.69292000e+03   8.77712200e+04   2.22740000e+03   9.14760000e+02
    1.10445000e+03   2.39714100e+04   6.10287100e+04   0.00000000e+00
    0.00000000e+00]]
[7066.3, 4951.0, 204664.31, 2027.6, 14498.4, 41686.4, 1077.0, 21773.37, 13321.7, 284136.73, 9401.6, 5247.4, 5802.0, 67727.5, 783031.81, 24.0, 66.0]
[1768.93, 2421.83, 84863.77, 70.04, 2571.77, 11872.19, 2.11, 3917.0, 1692.92, 87771.22, 2227.4, 914.76, 1104.45, 23971.41, 61028.71, 0.0, 0.0]

But running the same script with V. 3.9.7 produce different result (not the output what I want):

Test
1.3.4
[[1.768930e+03 2.421830e+03 8.486377e+04 7.004000e+01 2.571770e+03
  1.187219e+04 2.110000e+00 3.917000e+03 1.692920e+03 8.777122e+04
  2.227400e+03 9.147600e+02 1.104450e+03 2.397141e+04 6.102871e+04
  0.000000e+00 0.000000e+00]]
[1768.93, 2421.83, 84863.77, 70.04, 2571.77, 11872.19, 2.11, 3917.0, 1692.92, 87771.22, 2227.4, 914.76, 1104.45, 23971.41, 61028.71, 0.0, 0.0]

If in the code I changed header=0 to header=1, python 3.9.7 works producing the output as intended:

Test
1.3.4
[[7.0663000e+03 4.9510000e+03 2.0466431e+05 2.0276000e+03 1.4498400e+04
  4.1686400e+04 1.0770000e+03 2.1773370e+04 1.3321700e+04 2.8413673e+05
  9.4016000e+03 5.2474000e+03 5.8020000e+03 6.7727500e+04 7.8303181e+05
  2.4000000e+01 6.6000000e+01]
 [1.7689300e+03 2.4218300e+03 8.4863770e+04 7.0040000e+01 2.5717700e+03
  1.1872190e+04 2.1100000e+00 3.9170000e+03 1.6929200e+03 8.7771220e+04
  2.2274000e+03 9.1476000e+02 1.1044500e+03 2.3971410e+04 6.1028710e+04
  0.0000000e+00 0.0000000e+00]]
[7066.3, 4951.0, 204664.31, 2027.6, 14498.4, 41686.4, 1077.0, 21773.37, 13321.7, 284136.73, 9401.6, 5247.4, 5802.0, 67727.5, 783031.81, 24.0, 66.0]
[1768.93, 2421.83, 84863.77, 70.04, 2571.77, 11872.19, 2.11, 3917.0, 1692.92, 87771.22, 2227.4, 914.76, 1104.45, 23971.41, 61028.71, 0.0, 0.0]

but python 3.5.2 gets it wrong. what modification can be made to the code to make it work for both versions? Thanks for any feedback