Addition Formula works intermitantly

I have a simple PDF fillable net worth statement where the addition of two calculated fields does not add together correctly. The net worth statement consists of a "Value" column, a "Liabilities relating to that Value" column a "Net Value" column. Some of the values may be left blank if not applicable. The Net Value works fine (Value-Liabilities relating to that Value)
The net worth statement is broken into two sections (financial assets and fixed assets), with subtotals in each section. The subtotals work fine. The problem is with the net worth number where the subtotals for the two sections are added together for the Net Worth is the wrong number.
The net worth number sometimes works and sometimes doesn't. Also, when a number is removed in the top section from the Value column the correct total appears in the net worth field.
The statement has been working fine for the last 3 years and this issue just recently started.
I have not found anything in the Community that helps with this. Also, looked at the Set Field Calculation Order.
Any help or suggestions would be appreciated.
Thank you