[Question] MacBook Pro 4,1 - trying to boot from Monterey Installer but always boots into installed OS

I‘m trying to upgrade my MacBook Pro 4,1 from El Capitan, which is the latest officially supported OS, to Monterey using OCLP 1.5.0.

I’ve downloaded the installer through the app, but wasn‘t able to create a bootable USB with it so I used the terminal method using Apple‘s command. I built and installed OpenCore on both the internal drive and the bootable stick.

When holding shift upon booting I get the options for El Capitan, Recovery, and three EFI Boot options. One with the OpenCore Logo and the internal hard drive icon, one with the OpenCore Logo and the external drive icon and one with just an external drive icon. The two with the OpenCore Logo just boot into El Capitan and the one with just the external drive icon just shows me a circle with a slash.

I‘ve used OCLP in the past on my late 2012 iMac without any problems but I can’t figure out why I can‘t get MBP to boot into the installer. I’ve googled all kinds of things but am no wiser.

Could anyone help out, please?