The failure of a subtotal in an Access form has been a problem back in 2015. In summer of 2017, an automatic update of Office 2010 pro caused the problem to occur. About a month later the problem magically disappeared -- I suspect an update
ran a fix for this problem.
The Oct 2017 Office 2010 Pro update has returned the problem. Is Microsoft aware of the problem and can they fix it and prevent it from reoccurring with subsequent updates.
Form footer contains a subtotal calculation. This no longer produces the value, instead the result is null.
The database in question has several form that use this design feature. It is a problem!!!