After submitting the form, the site starts to break down, how to fix it?

Question

JavaScript

Website crashes after submitting form

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and when you try to refresh the page, nothing practically changes and only this message appears

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I think that you can just do it so that when the page loads, the site always becomes exactly through js, but that message and, in general, the problem itself will not go away. So
, can someone know how to fix this?

here is the site:
https://scandium.com.smw.area.lv/