Q:

SharePoint 2007 - InfoPath form library not allowing new items

I am in a very strange situation,  and have been working with Microsoft Support on the same.  With not much results.
We had a site in SharePoint 2007 with a InfoPath form library,  we had migrated this site to SharePoint 2013 and everything has been working perfectly.
This library currently have 4896 forms in it,  When i try to add another form in this library I get an error saying

form can not be submitted,  the site can not be found

When i delete few items from the existing library I am able to add new forms (exactly the same number of forms).  I have also created a new empty library by saving existing library as template.  And I am able to save the forms in the new library without any issues.
Notice the icon difference between the library that was migrated (v2) and the new library that was created by saving the same library as template (v3).

We have disabled threshold for this library,  increased quota for the site and increased threshold for the web application,  none of it is allow me to save any new form to the old library.
We also uploaded more number of forms in the new library (v3) and i am able to upload there without any issue.
I looked at the size and we had more data in (v3)

We are trying to identify if we had any hard limit in the SP2007 Form Libraries that is preventing us from uploading new forms.
I even tried exporting the (v2) forms and importing it onto (v3),  however looks like we do not have any option of importing forms onto a different library.
Any suggestions/information on the form library limit?  Please help

A:

We resolved this issue ourselves,  it had nothing to do with InfoPath library size limit or anything else.  
Our form used to create new items using an ID,   which was calculated based on the existing number of items.
Once of the user had created a draft version of InfoPath form and which as some id,  since the form was never checked-in,  all the new forms used to get the same ID and were not able to save data. Once we checked-in the files everything started working.
The biggest problems have easiest solutions... :)
But this is something to keep in mind,  error messages were taking us to all the wrong directions...

