title: Sheets gets stuck Loading... a cell and I have to reload
body: <p>tl;dr: My custom-formula cells all go Loading... and they start filling in results, but they get stuck. A reload immediately provides the completed results. I don't want to reload every time I change a value.</p>
  <p>In my sheet almost all cells are interconnected, so changing one cell triggers a recalc. Each row is a year, each column is an identical formula across all rows. Each cell can refer to earlier columns in its row or anything on the prior row, plus a few absolute locations containing the &quot;inputs&quot;. Changing an input triggers a recalc of everything.</p>
  <p>The column with my custom function will go Loading..., then one cell at a time it returns the value, almost one second per cell. OK, slow, but fine. But often it just stops completely partway down. Sometimes it starts up again, but often it never does.</p>
  <p>But the cells WERE all recalculated. My custom function was called and returned values promptly, execution time of 0.125 secs or less usually. If I reload in the browser, I immediately get the fully recalculated sheet. It looks like some link is being severed between Sheets in my browser and Google's servers, so I stop seeing updates.</p>
  <p>This is the first time I've ever used Apps Script -- or JavaScript for that matter -- but I have been programming in other ways for decades. If it matters, the custom function is purely mathematical, calling no services except Math, not even Spreadsheet, getting everything it needs in its arguments, using a few functions in the same file. It's a detailed taxes calculator.</p>
  <p>I'm using a recent Chromebook.</p>