Having intermittent issues remapping certain keys following <leader>

[Elyviere]

Hi.
I've got a few issues with mapping certain keys. These are the two that aren't working properly:
map <leader>iv <Action>(IdeaVim.ReloadVimRc.reload)
nmap <leader><tab>l <Action>(GoToLastTab)

The issue with these remaps is the second character, i.e. the 'i' and the '<tab>'. The 'i' map usually works immediately after reloading the .vimrc, but will suddenly stop working and instead enter insert-mode when I press <leader>i. In case it matters, I've remapped <leader> to <space> with let mapleader = " ", but I'm able to reproduce these issues using the default mapleader as well.

The <tab> one does something similar, and only works sometimes. Other times it puts me in some sort of weird state where I can't control the cursor properly until I ESC.

Also, I haven't figured out how to add <leader><tab> to WhichKey, the following hasn't worked. WhichKey properly shows up when pressing , but closes when I press :
let g:WhichKeyDesc_tab_last = "<leader><Tab>l Last Tab"

Is anyone else able to reproduce these issues, i.e. are they bugs, or do these remaps work properly for other people?