AEM Forms 6.5.17 - Index value out of range error

[CØK]

We were just updated from 6.5.0 to 6.5.17. We are unable to save or generate PDF preview for some forms, getting the log error "Index value out of range". There are no scripts on the forms. The error gives no indication of where the problem lies - no object or line info. Forms are also not, and have never been, attached to any kind of database. They are simply designed and published for the public to download. I tried copying individual objects into a new form, saving each time to see if I can isolate the error - no error was generated. 

Please tell me there is a simple fix.

Oh, and this is only if saving the form as a static PDF, a must for the format we post our forms in. Dynamic does not seem to have a problem - but still can't generate PDF preview. If saved as XML form, it all works.

7/26: I have more info: The problem occurs when you have a grouping inside a List Item inside a List. Unwrap the List Item, and preview can generate OR Ungroup the grouped item, preview can generate. This does still seem like something that needs to be fixed. 

[EstebanBustamante]

Could you review the logs to identify additional clues regarding the problem's source? Since you were able to successfully migrate to a new form without any issues, it suggests that there might be some form corruption. The logs could potentially indicate the specific areas where this problem arises.

[CØK]

Found one more clue - the problem seems to be connected with grouping. Not all grouping, though. Could it have to do w the reference “#area”?

[CØK]

The log does NOT generate any useful info:

Generating PDF Document...
Index value is out of bounds

As I stated above, there seems to be some conflict w grouping inside a List Item subform.

[Mayank_Gandhi]

@CØK is this happening in designer preview?

[CØK]

Yes - we can't generate PDF preview when designing a form. We also cannot save the form as a static PDF.

[kautuk_sahni]

@CØK Did you find the suggestions from users helpful? Please let us know if more information is required. Otherwise, please mark the answer as correct for posterity. If you have found out solution yourself, please share it with the community.

[CØK]

There is no solution in any of the answers, so cannot mark any of them correct. There is my own workaround which is to remove grouping inside subforms.