Not remembering Chart labels

I have recently a very strange issue. In one of my spreadsheets I have a number of charts, defined in Tables, and they work fine. However when I close and reopen the workbook, the charts labels are replaced with the values of the corresponding range. I have to redefine the charts again, by selecting the source, to get the names visible again.
Unfortunately this sheet is too big (and too confidential) that I can upload this.

Is this a known issue and how can I solve this?

Cheers
Erwin

Obviously you know it is very hard to diagnose issues without seeing the workbook. Whilst it might tke a little bit of effort, it really would be wise of you to create a copy of the workbook with most of the data removed and the remaining data desensitised. We only need to see one chart displaying the behaviour.

Yes, you are completely right. Unfortunately I cannot reproduce the problem if I make the same chart on a new workbook.
And after copying the worksheet to a new workbook: Excel crashes everytime. (probably due to cellreferences to other worksheets).
So the solution is very local and I will have to look into my workbook itselve

Thanks anyway for the suggestion!
Cheers
Erwin