I have had a very nasty bug that I debugged in Safari. Chrome & Firefox supports redirects to http when the site is on localhost or 127.x.x.x but Safari doesn't and throws a Mixed content warning error.

Another one was similar when redirect chain got broken because of an intermediate redirect (https -> https -> http -> https)

I guess Chrome & Firefox automatically upgrades the protocol now but Safari doesn't and it broke the chain and it was also not showing the broken redirected chain in the Safari developer tool.