I have an image that shows this info with exiftool

exiftool frame_0003.png
ExifTool Version Number         : 11.88
File Name                       : frame_0003.png
Directory                       : .
File Size                       : 18 MB
File Modification Date/Time     : 2024:06:02 13:08:17+02:00
File Access Date/Time           : 2024:06:02 13:08:13+02:00
File Inode Change Date/Time     : 2024:06:02 13:08:17+02:00
File Permissions                : rw-r--r--
File Type                       : PNG
File Type Extension             : png
MIME Type                       : image/png
Image Width                     : 3840
Image Height                    : 2160
Bit Depth                       : 8
Color Type                      : RGB
Compression                     : Deflate/Inflate
Filter                          : Adaptive
Interlace                       : Noninterlaced
Pixels Per Unit X               : 0
Pixels Per Unit Y               : 1
Pixel Units                     : Unknown
White Point X                   : 0.3127
White Point Y                   : 0.329
Red X                           : 0.64
Red Y                           : 0.33
Green X                         : 0.3
Green Y                         : 0.6
Blue X                          : 0.15
Blue Y                          : 0.06
Gamma                           : 1.961
Exif Byte Order                 : Big-endian (Motorola, MM)
X Resolution                    : 72
Y Resolution                    : 72
Resolution Unit                 : inches
Y Cb Cr Positioning             : Centered
Exif Version                    : 0232
Date/Time Original              : 2024:04:26 14:24:50
Components Configuration        : Y, Cb, Cr, -
Flashpix Version                : 0100

I tried to modidied the Date/Time to add milliseconds using

exiftool -d "%Y:%m:%d %H:%M:%S.%3f" -overwrite_original -DateTimeOriginal="2024:04:26 14:24:50.100" frame_0003.png

while the commands does not give any errors, this does not modify the time stamps in the metadata.