I have 4 OS's install , windows, mint, mint xfce, and manjaro; when I install an OS, I always disconnect all of the other drives, so what ever OS is in it , is contain on that hard drive only, there for I can boot from any of them ; if I start manjaro first it boots correctly and I can boot any other OS from there also , but if I start any other first , manjaro goes into kernel panic .
Manjaro (and Arch) use two arguments on the initrd line in grub.cfg. Most other distros expect only 1. The newest grub can support 2(+?) arguments, but most non-arch distros are still using an older grub. The panic is because the second argument is half of the kernel. Half of linux won't start. A few non-arch type distros do have the newer grub.
The recommendation is to make Manjaro's grub 1st in boot order. If that is not feasible, then add a custom.cfg to the other distros to add a manual menu entry for manjaro (suggest the grub command configfile.) A search of the forum for "custom.cfg" yielded these ideas to make a custom.cfg. Just add it to /boot/grub/ for each distro that panics on loading Manjaro.
thanks for making it clear, for me is ok that manjaro starts firs, is just as fast as linux or maybe a tad faster, I was a little concern that maybe it was showing some sort of instability ,thats all ; thanks again