Here is an issue I have experienced after manually installing formEmailer into a new sheets/form.
After copy/pasting script into new .gs file, and running authorization and install, everything set up fine. I then added formSubmit trigger to method timeDriven. I then proceeded to advance settings and defined a formula column. Everything was looking good.
When I submitted a form, what happened was after sending the email to the form submitted row, the script continued to attempt sending an email for every blank row in the sheet. It was going crazy! I quickly deleted all the blank rows (the default in new scripts is 1000), and it stopped.
Not sure why this works differently in new sheets, but I would advise any users attempting a manual install into new sheets, to be sure and delete any extra rows before running script. Not sure if this was caused by formSubmit trigger, or something else.
On a second form submit trial, it worked just fine.