It is normal, and even expected, for some of your Google Sheets formulas to reset periodically, for example, at the beginning of each week or month.
Depending on your formula, that reset could be to either zero (0) or blank (empty cell). Again, that's perfectly normal and even anticipated. However, the difference between 0 and an empty cell can be meaningful in the sense that 0 will display a 0 on your widget (see right image), and an empty cell will show "No data to visualize" (see left image).
To protect against errors in your spreadsheet, wrap your formulas using IFERROR. For example, use A instead of just B.
=IFERROR(QUERY(Calculations,"select count(A) where E is not null and N matches '"&Calculations!$R$2&"' and E like '%"&A2&"%' label count(A) ''"),0)
=QUERY(Calculations,"select count(A) where E is not null and N matches '"&Calculations!$R$2&"' and E like '%"&A2&"%' label count(A) ''")
Let's say that you have a number widget powered by a cell B2 and B2's value is
=A2. Instead, we'd recommend using
=IF(ISBLANK(A2),0,A2). This way, if A2 is empty, the cell that powers your widget will default to 0 instead of also being empty, which will result in "No data to visualize".