“End of script output before headers: index.php” Error on Joomla Site

A non-regular client of ours, after updating their Joomla website to 3.9.1 a couple of weeks ago, started seeing the following classical error on their homepage: Internal Server Error What was interesting was 2 things: 1) the error didn’t happen immediately after the update, but rather a few hours later, and 2) the error disappeared […]