[JamOfBoy]

Appling Chimera Install to a youkai that subsequently dies will prevent you from accessing the Chimera Install-ee youkai's... anything.

Example:
Summon Apus.
Chimera Install Snow Crow onto Apus.

Apus perishes.
You can no longer Cresyr. You still have Snowfall, but given Snowfall's odd nature, this is likely an outlier. I'd imagine with any other youkai, you'd get none of it.

This can be recreated as such. An important thing to note that in my own tests, I had the Shapeshifter install duration innate. Chimera Install locks the install-ee youkai out, with the lockout status. This lasts for 3 round, but the install does not. Snow Crow is locked out, but... also installed, and both of these things prevent you from using it. This could be involved in the issue.

This also leads into a bigger issue, where once this happens, there's a high chance the installee youkai will become a phantom.
It'll show up in the list, it'll be fully healed, but you won't have access to any of it's abilities. You won't be able to summon, install, anything, and this will persist between fights.

I can show screenshots if needed.

[Neus]

This should be corrected in 2.64.