Lost session

Just to throw in a few more random variables into the mix...

I'm on PHP 7.3 & CI 4.0.0-rc.3 (and experienced a similar problem on CI 4.0.0-rc2 too)- whereby, if the user mistypes the address and the rerouting doesn't work out where to send the request, CI automatically redirects to the 404 error page... and every bit of session data seems to disappear.

I've not spent a lot of time trying to work out what's happening, though sessions have been working without a problem (without me having had to fiddle with any of the settings (so everything is as it came/default/out the box))...

Here's another bit of useless chaff, that will probably only muddy the water... if I remember correctly, I believe I previously experienced the same problem of losing session data when using the redirect() command in my code... but manage to side-step the issue at the time by using other ways to call the new page (without using the redirect() command directly).