With Windows 2019 and IIS10 with an SSL certificate installed. The problem is that every page on our site is loaded twice by Firefox when called up on https. We started noticing this because form submissions would start throwing unique constraint errors after trying to do an insert twice. Or we have some buttons that send email reminders and those will send two emails. as a solution we have disabled http / 2 from the ISS bingind, it is possible to have a solution without such disabling. This behavior is only with Firefox while other browsers do not have it. thank you