Hi there, It looks like you are using directory for default language as well but setting Home URL to hidden link and not using any root page which seems to cause the issue here.
Can you please set both your WordPress Address and Site Address at wp-admin -> Settings -> General to hidden link then use a root page as explained in the following document instead:
The problem might be caused by the absence of root page, which I didn't set up previously. Now I generated a root page, which is redirected to the main language main page, as described in the document. So far it works ok, I hope it will remain even after an automatic generation of the .htaccess file. Thank you for the help!