ERR: 522 circualar ref in =sum()

I am trying to SUM the values in a column and am getting ERR: 522, circular reference. The data in the column being summed is created via VLOOKUP. Would this cause the problem?

Edit: The VLOOKUP pointed to a different sheet. When I moved the VLOOKUP to the same sheet it works fine. Is this a bug?

Please upload your sample file here.
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“Err 522” means: the Result Cell is located (directly or indirectly) in the input parameter list of the formula of the Result cell.

No, not directly. But, if your VLOOKUP includes the cell of the SUM you may create a circular reference…
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Usually there was a bug/mistake/error in YOUR formula, not in Calc. There are bugs in Calc, but usually the most common source of errors in sheets is found by looking in the mirror.
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If you actually seek help here the minimum information we need is the used formula, in your case the complete sheet, wich shows the error.
If your error is gone now and you have not kept the previous version, there is no way to find this out…

It appears I have changed whatever was causing the error and cannot get it to repeat.