My boot-duration file is correctly formatted, so I think this was fixed.
root@Jarvis:~# cat /var/lib/plymouth/boot-duration 0.517:fsck:/:100 0.517:fsck:/boot:100 0.619:7 0.621:14 0.646:22 0.659:29 0.663:36 0.670:44 0.674:51 0.675:58 0.676:66 0.763:67 0.767:69 0.771:70 0.779:72 0.816:74 0.819:75 0.865:77 0.867:79 0.940:80 0.942:82 0.945:84 0.946:85 0.954:87 0.958:89 0.967:90 0.987:92 0.995:94 0.996:95 0.996:97
My boot-duration file is correctly formatted, so I think this was fixed.
root@Jarvis:~# cat /var/lib/ plymouth/ boot-duration /boot:100
0.517:fsck:/:100
0.517:fsck:
0.619:7
0.621:14
0.646:22
0.659:29
0.663:36
0.670:44
0.674:51
0.675:58
0.676:66
0.763:67
0.767:69
0.771:70
0.779:72
0.816:74
0.819:75
0.865:77
0.867:79
0.940:80
0.942:82
0.945:84
0.946:85
0.954:87
0.958:89
0.967:90
0.987:92
0.995:94
0.996:95
0.996:97