code is working in chrome, not in firefox

[schoormans]

the data that is put in the html form, is send through a php file to store in a json file. when the user, has paid, they are send to a php file the php file takes the data out of the json file and uses it. it is working great in chrome. but in firefox the data is not being send. here is my html form and the `

Naam:
Datum:
Email:
Taillewijdte (in mm):
Heupwijdte (in mm):
Heuphoogte (in mm):
Bovenwijdte (in mm):
Lichaamslengte (in mm):
Bustediepte (in mm):
                                     
`

[schoormans]

this is my webpage https://patternsbyanoukschoormans.com/z123shirt.html

[JakeChampion]

This doesn't look like an issue related to this fetch polyfill to me