Whatsapp picture file names

Hello everyone, I'm looking for some guidance on the below issue!

My iphone 7 (iOS11.3 ) saves photos taken by the camera sequentially following the format of IMG_0001 ascending.

When someone sends me a picture via Whatsapp, I have it set to save automatically into my Photos folder. Using the app called Investigator I can see that the file names of these pictures are following the same format as above (IMG_0001 etc), HOWEVER, when I upload all my pictures to my desktop (windows), the photos that originated from Whatsapp now have longer randomised names such as PUKB3320. The IMG file name that I can see through Investigator is nowhere to be seen in the properties of the picture once it is uploaded to the computer.

This didn't used to happen, but I'm not sure what has changed. Does anyone know why the file names are changing at the time of import? I'd prefer to go back to having all of my photos follow the IMG_0001 naming convention, if that is possible. Can anyone offer a fix?

Thanking you in advance!

Jess