Following on from my recent upgrade of Nintex Forms 2013 to version 2.9.4.0. There have been a few problems affecting multiple forms.
One was with the SQL Request control and calculated fields.
https://community.nintex.com/thread/15053-sql-request-action-and-calulation-field-bug-work-around
I now also am getting reports of forms failing to open which have lookup fields connected to the root site. These are erroring and I have to go into each form and reconnect the lookup field to the list.
It seems to only affect lookups connected to the top site "/" and where the lookup isn't connected to the lookup field. IE just populating a text field with the result.
Update 10/02/2017
Another small issue. People picker fields. If they are close to fields below, the drop down is getting obscured by the field below.
The fix is simply to bring the people picker to the front.
Logging with support.