Should they be warned or somehow restricted for a time?

Not by you, as you don't have the power to restrict users, and you don't have enough authority to issue a warning.

The best to can do is flag/close as a duplicate and/or raise a custom flag on the post(s) for moderators to review.

They are receiving similar answers, but don't agree with or accept any of them.

The participation of a user with regard to answers on their own question is irrelevant in my opinion. A user is free to not be satisfied with answers on their questions, no matter how unreasonable their opinions actually are.

Should they be warned or somehow restricted for a time?

Not by you, as you don't have the power to restrict users, and you don't have enough authority to issue a warning.

The best to can do is flag/close as a duplicate and/or raise a custom flag on the post(s) for moderators to review.

They are receiving similar answers, but don't agree with or accept any of them.

The participation of a user with regard to answers on their own question is irrelevant with regards to how this situation should be approached in my opinion. A user is free to not be satisfied with answers on their questions, no matter how unreasonable their opinions actually are. And if a user is posting similar questions, the reason why they are doing this doesn't affect that it shouldn't be done.

Should they be warned or somehow restricted for a time?

Not by you, as you don't have the power to restrict users, and you don't have enough authority to issue a warning.

The best to can do is raise a custom flag on the post(s) for moderators to review.

They are receiving similar answers, but don't agree with or accept any of them.

The participation of a user with regard to answers on their own question is irrelevant in my opinion. A user is free to not be satisfied with answers on their questions, no matter how unreasonable their opinions actually are.

Should they be warned or somehow restricted for a time?

Not by you, as you don't have the power to restrict users, and you don't have enough authority to issue a warning.

The best to can do is flag/close as a duplicate and/or raise a custom flag on the post(s) for moderators to review.

They are receiving similar answers, but don't agree with or accept any of them.

The participation of a user with regard to answers on their own question is irrelevant in my opinion. A user is free to not be satisfied with answers on their questions, no matter how unreasonable their opinions actually are.