order-received page error for multilingual shop

Hello,
I’ve been running my woocommerce shop on a multilingual site using WPML.
When clients check out in the main language, english, everything goes smoothly.
When they check out in the other languages, dutch or french, then the order-received page after succesful payment returns a 404 error, like this:
https://botanopia.com/panier/validation/Commandere?ue/7008773/?lang=fr&key=wc_order_PQszGnOr0uHXj&utm_nooverride=1

for reference, a succesful order in english returns this page
https://botanopia.com/cart/checkout/order-received/7008689/?key=wc_order_Lm5Kddb0o091R&utm_nooverride=1

This means clients who order in french/dutch get no confirmation email, and the order does not get set on “processing”. Clients get worried, and i end up with lots of complaints emails and chargebacks on the payments.

I’m guessing something’s not set right regarding the order-received pages?
I hope someone has had the same and knows how to fix it?
Thanks

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