Try to check on DB level.
This SQL should give a list of all spam comments (which I assume skräpposter means):
SELECT * FROM `wp_comments` WHERE `comment_approved` = 'spam';
If the SQL gives 0 lines, the issue is with WordPress counting those comments, but in fact there are none. If the SQL gives a list, the issue is with the listing of those comments.
It may be an issue with the term spam being translated when writing comments to the db, but not when reading or vice-versa. You can check all approval status tags in your db using this:
SELECT DISTINCT `comment_approved` FROM `wp_comments`;
(or in some dialect: SELECT UNIQUE `comment_approved` FROM `wp_comments`;)
This should show terms like 1 (approved), 0 (pending), spam, trash etc. If you see translated string here, like skräpposter and similar, you may be in for a ride to find out why those terms are not written in the db as they should.
If all seems fine on the db level, it’s trickier to find the reason, why those are not listed. Definitely needs the target system to be investigated more.
But anyway, this is where I’d start my investigation.
*: assuming your db prefix is wp_
Also:
It may be a malware infection, which may benefit from removing your ability to manage comments. They could as well hide spam comments from logged in admin user on the frontend, while showing them to regular visitors, so check your site in incognito and probably run some kind of a malware scan on it too!