Google Merchant gets the wrong Currency and Price

Some of our producs get denied by Google Merchants crawler sometimes. When their bot crawls the page it sometimes thinks that the price (and currency) differs from our submitted Google Merhcant XML feed. We get the message:
Mismatched value (page crawl) [price]

This seems to be due to a JSON-LD feed that gets generated a plugin that we use: “Google Tag Manager for WordPress” By Thomas Geiger. This plugin most often get the price and currency right. But sometimes it doesnt (says google).

Google insists that the JSON feed sometimes shows the original price in SEK, instead of the EUR price that is displayed in the html.

I first thought this could be because of the “Switch Currency by JS” option. So I turned this off. And I also added &wmc-currency=EUR to our links in the Google Merchant XML feed. So now we do get the right price, by php, from the start. Google doesnt seem to care about that though, as there is no Structured Data markup in the HTML for that. Like this: https://schema.org/Offer

This is an example of our products that keeps getting denied:
https://thunderfitness.com/fi/voimaharjoittelu/kasipainosarja-35-kg/?utm_source=Google%2BShopping&utm_medium=cpc&utm_campaign=google_shopping_fi_01&wmc-currency=EUR

Is this an issue you have faced before? Do you know what can be the cause of it?

Is there any way to make sure that “Google Tag Manager for WordPress” gets the right information? Maybe there is a miss match in the hooks they are using? I will contact them as well about this. Is there something they need to know to make it compatible with your plugin?

Or do you have another solution? Maybe try removing the price and currency in their JSON feed and adding it to a custom made on our own?