Provided that this use-case is a bit peculiar for me, so I hope some else will have better ideas , I think the following information might be beneficial anyway:
garuda-inxi
efibootmgr
When this issue started (did the triple boot work until a certain point)?
This is also useful to understand how the dual boot of the two garuda systems was handled.
If you do not take specific steps, you risk the second installation to overwrite the grub of the first one. See e.g. here:
, I think the following information might be beneficial anyway: