Form submission with empty fields is not stopped by validation

In my Laravel 11 application form submission with empty fields is not stopped by validation. What drives me crazy is that the same app - the same deployed code - works absolutely correctly in quite a few installations without ANY problem. If I leave empty fields I get the validation error messages and the form is not submitted. In the one problematic site, by clicking submit, the form is submitted (is it really submitted?) and the next I get is a 419 Page Expired error. I deleted all the contents of the deployed laravel code and re-transferred everything inside the app folder but the same thing happens. It is a simple form with the code below:

        <div class="col-sm">
            <div class="form-group">
                <label for="doctitle"><strong>Name</strong></label>
                <input type="text" class="form-control" id="doctitle" name="doctitle" value="{{ old('doctitle', $doc->doctitle ?? '') }}"  placeholder="Please enter your name">
                @error('doctitle')
                <span class="text-danger">{{$message}}</span>
                @enderror
            </div>
        </div>

      <div class="d-grid gap-2 d-md-flex">
        <button type="submit" name="action" value="saveandclose" class="btn mt-3 mb-5 btn-outline-primary">Submit</button>
    </div>

      <br>

    </form>