Here's what happened:
I have two hard drives in my computer ( I will refer to them as nvme0n1 and nvme1n1p1, since those are their device names ). On one harddrive, nvme1n1, I had installed Fedora as my main distro. I have used it for a few months.
Since I initially came from Manjaro, and greatly value the Arch ecosystem, I decided to install Manjaro alongside Fedora. I did, however, not want to split up the hard drive which Fedora -nvme1n1p1- was installed on, an decided to install Manjaro on my second drive, nvme0n1.
I downloaded Manjaro i3, since I am used to tiling window managers.
Since I did not want to change the boot order in my Bios every time I'd decide to boot Manjaro, I chose during the Calamares install to install the bootloader on the Master Boot Record of nvme1n1p1, the drive Fedora was installed on, so I could simply switch between the two distros. The install completed successfully.
At first glance, everything seemed to be alright in the grub boot menu. Both Manjaro and Fedora were available. Manjaro booted fine. Fedora, however, didn't.
When trying to boot into Fedora, I got the following message: "error: file '/boot/initramfs-4.19.2-300.fc29.x86_64.img' not found."
Since I can choose which version of Fedora I'd like to boot (kernel-wise) under "Advanced Options for Fedora", I tried to boot the "Rescue" version, which worked. It takes ages to boot the rescue version, though.
What exactly is wrong? Since I can verify that the OS is completely fine by booting into it in rescue mode, it must be a misconfiguration of grub, right?
Is there a way to fix this manually?
I'd appreciate any guidance