I’ve had similar issues with Keyscape - immense load/unload times and actually C3 crashes from time to time - Keyscape keeps a ridiculous amount of file handles open. See here: https://community.cantabilesoftware.com/t/ridiculous-number-of-file-handles-in-keyscape/4701
I ended up thinning the sounds (in the mix you don’t hear the difference) and I preload everything. Given that I’m pretty happy with Keyscape now.