Time-driven trigger (daily) not triggering every day - google-apps-script

Question

I have the similar issue as described at How to make sure a daily time trigger runs?.
I have a specific script in one of the Google sheets with a daily trigger (time-driven, should trigger every morning, set up through interface, not programmatically). But the script doesn't execute every day. I can see this in the execution report, where there're just successful executions and no failed ones. I can also see if the script executed by checking a cell in the sheet which gets updated with the execution timestamp when the script runs. And I've set up an immediate notification for the failed executions in the trigger settings.
In my specific case, the script should ran every day from Nov 9 - Nov 13, but it ran just on Nov 9, Nov 10, Nov 12. And I didn't get any notification about the failed execution.
The script itself doesn't use any API, it's pretty basic: reading data in one sheet, doing some calculation and writing to another sheet (talking about the sheets in single Google Sheet file).
If I run the main function manually, it always works.
I'd be very glad to get some ideas what could be wrong. Thanks.
EDIT: Code sample (main function and prototype for Array.includes)
function main(){
var date = new Date();
//var date = new Date(2019, 9, 1); // year, month (zero-indexed!!!), day
//var date = new Date(date.getYear(), date.getMonth()-3); // testing
var currentDay = Utilities.formatDate(date, "CET", "d");
Logger.log('currentDate: ' + Utilities.formatDate(date, "CET", "YYYY-MM-dd HH:mm:ss.S") + ' | currentDay: ' + currentDay);
if (currentDay == 1) {
Logger.log('currentDay is 1st of the month');
date = new Date(date.getYear(), date.getMonth() - 1);
var newCurrentDay = Utilities.formatDate(date, "CET", "d");
}
var monthToCheck = Utilities.formatDate(date, "CET", "MMMM").toUpperCase();
var yearToCheck = Utilities.formatDate(date, "CET", "YYYY");
Logger.log('dateToCheck: ' + Utilities.formatDate(date, "CET", "YYYY-MM-dd HH:mm:ss.S") + ' | monthToCheck: ' + monthToCheck + ' | yearToCheck: ' + yearToCheck);
var firstProjectRow = 7; // first row with the project data
var firstProjectCol = 1; // first column with project data - should contain Tool IDs
var numOfProjectRows = 999; // num of project rows to check (counted from and including var firstProjectRow)
var numOfProjectCols = 21; // num of project columns to check (counted from and including var firstProjectCol the last one contains number of hours for the last service)
var firstProjectHoursCol = 7; // first column with data about project hours (usually PM hours)
// ************* DO NOT EDIT BELOW THIS LINE ************* //
//return;
var indexedFirstProjectHoursCol = firstProjectHoursCol - 1;
var ss = SpreadsheetApp.getActiveSpreadsheet();
//var sheet = ss.getSheets()[3];
var sheetName = monthToCheck + ' ' + yearToCheck;
var sheet = ss.getSheetByName(sheetName);
Logger.log('sheet: ' + sheetName);
var range = sheet.getRange(firstProjectRow, firstProjectCol, numOfProjectRows, numOfProjectCols); // getRange(row, column, numRows, numColumns)
var rangeValues = range.getValues();
//Logger.log('rangeValues: "' + rangeValues);
var toolData = new Array();
var toolIds = new Array();
var toolHours = new Array();
//return;
for (var row in rangeValues) {
Logger.log('row: "' + row);
var clientId = rangeValues[row][0];
var projectId = rangeValues[row][1];
var hoursSum = 0;
// we have Tool ID so it's OK to proceed
if (clientId != "" && projectId != "") {
var clientProjectId = clientId + "-" + projectId;
for (var col in rangeValues[row]) {
var cellValue = rangeValues[row][col];
//Logger.log('col: ' + col + ' value: ' + value);
// get hours sum
if (col >= indexedFirstProjectHoursCol)
hoursSum += typeof cellValue == 'number' ? cellValue : 0;
}
//Logger.log('hoursSum: [' + hoursSum + ']');
var record = {id: clientProjectId, hours: hoursSum};
Logger.log("Data: " + record.id + " : " + record.hours);
// don't yet have a record of clientId-projectId
if (!toolIds.includes(clientProjectId)) {
toolData.push(record);
}
else {
recordIdx = toolIds.indexOf(clientProjectId);
toolData[recordIdx].hours += hoursSum;
}
toolIds = [];
toolHours = [];
toolData.forEach(function(item) {
toolIds.push(item.id);
toolHours.push(item.hours);
});
}
//Logger.log(toolData);
//Logger.log('ROW DONE!');
}
Logger.log('ROWS DONE!');
Logger.log('toolData.length: ' + toolData.length);
toolData.forEach(function(item) {
Logger.log('toolData: ' + item.id + " : " + item.hours);
});
Logger.log('DONE!!!');
// fill the table in the sheet with assigned number of hours
fillTheSheet(sheetName, toolData);
}

Answer 1

Apps Script triggers have always been a bit finicky. But of late they have been far more unreliable than usual (there have been several reports of spurious triggers and other maladies).
In this case, you can avoid using them altogether by leveraging an external service such as cron-jobs.org.
You'll have to refactor your app script project and deploy it as a public Web App with a doPost(e) function. You'd then pass the Web App's url to the external service as a web-hook endpoint that is invoked daily.