My problem is not so much freezing, but when printing a new custom template on an older SO (one that was created before the template) many fields are blank. Specifically, it seemed the custom fields in the inventory file is not recognized by the new template. 

In my case I created a great Packing List Template, adding 4 custom item fields (Carton #, Color, Size etc.). When I go to a previous Sales Order (one that was created before the new template) select the new custom Packing List Template, the 4 custom item fields are not showing on the Print Preview.

FYI Each item on the older Sales Order has had the 4 custom item fields filled out long ago, but do not show up on new template.

FYI2 - I am following this workflow to create a new template: In a Sales Order > Formatting > Manage Templates > Additional Customization > Select the columns from the column list I want (many from the custom inventory fields) and change the layout of each column.