Variable 'root' isn't set error when trying to instal manjaro

Im trying to install manjaro linux (first ever linux install other than debia on my raspberry for me) on my old laptop (fujitsu lifebook s751). I created a bootstick with the manjaro kde iso from their official website (the iso works inside of a virtual box on my windows pc). When booting from said stick i get the following message:

error: variable `root´  isn´t set.
Entering rescue mode...
grub rescue> 

I am 99.9% sure my bootstick isn’t the problem. I redone the bootstick multiple times with each etcher and rufus (which told me it switches to dd mode automatically due to the nature of the iso) and on another machine the stick works without a problem and the installer is launched on boot.

`ls´ delivered me with (hd0) and (hd1) and apparently (hd0) is my bootstick (ls (hd0)/ gives me back a filesystem whilest with ls (hd1)/ i get error: unknown filesystem)

I tried following instructions from this thread: askubuntu .com/a/563648. But the commands linux´ as well as initrd´ and boot´ gets me a unknown command´ back.

The laptop has a intel i5-2520M (2.5GHz), 4GB ram and a 350GB HDD.

What causes this problem and how can i fix it?

To get your confidence about your bootstick from 99,9% to 100% verify if it’s working when preparing the stick using dd:

Also, please let us know how you boot the stick - in UEFI or BIOS mode. Manjaro’s ISOs are of hybrid design, the allow both.

the verification steps of etcher and rufus both told me everything was good. I’ll try verifying manually it. How can i find out if it is in BIOS or UEFI mode? Im not sure but i think my laptop has BIOS only. But again im not sure how i can check if my assumption is correct.

There are too many different firmwares I could help you, check mainboard documentation or verify all the options you have in your firmware. If your firmware allows both you usually have two boot entries for the stick, one having UEFI at the begin of the entry name.

I checked an online manual for the laptop model and it seems to only feature BIOS. Also there is only one boot option for the stick.
Also i was not able to manually verify the bootstick on my windows machine, but as i said i used rufus and etcher to verify directly after installation and everything was fine.

As you haven’t answered yet i have tried a workaround idea i had: I used my other laptop to install manjaro onto the disk and for now it is working. Still i don’t think this is how it should be done so message me if you want or need more information and if we could find an actual solution for this. I would very much appreatiate that.