Invalid JSON. Unexpected end of input was found in JSON content. Not all object and array scopes were closed

Question

I receive this message when I try to get PORDER EXTFILES. I get the 'Invalid JSON' error when I try to parse the message.

The request is: /PORDERS('PO24000090')/EXTFILES_SUBFORM

In the response I get an uncompleted json which looks like this: {"@odata.context":"[ServiceUrl]/$metadata#PORDERS('PO24000090')/EXTFILES_SUBFORM","value":[

It worked fine and it seems that it started to happen when some data has been modified in Prioriy forms.

What can it be ?