Hi, weird error while trying to create a simple search result page:

var filteredQAs = rootNode.Descendants("KBQAItem").Where("author.Contains(@0)", "יעקב אריאל");
filteredQAs = filteredQAs.Where("title.Contains(@0) || text.Contains(@0) || imgText.Contains(@0) || question.Contains(@0) || Author.Contains(@0)", searchString); 

...

@foreach (var qa in filteredQAs.OrderBy("updateDate desc").Skip(currentPageNo * NumberOfItemsPerPage).Take(NumberOfItemsPerPage))
    {
        <div class="kbRow">
            <a href="@qa.Url" title="@qa.title">
                <h3>@qa.title</h3>
            </a>
            <div class="author">@qa.author</div>
            @Html.Raw(Umbraco.Truncate(Umbraco.StripHtml(qa.question), 300, true))
        </div>
    }
...

some of the links created just fine with nice URL, but some of them gets a #err-18040 (= this node Id...) href and I have no Idea why...

If I try to just use @Umbraco.Content(18040 ).Url instead of @qa.Url it works fine, but @Umbraco.Content(qa.Id).Url doesnt... Where do this "#err- ..." comes from?!?!

Its a big website (>20K nodes) started from umbraco 4 and upgraded every few monthes all the way to the current umbraco 7.5.2. There is also a standard URL ReWriting to add an www and the 's' https, but nothing special...

Any Idea?