If the drive that holds your sample libraries is formatted to APFS or ExFat, Kontakt won't be able to retrieve data fast enough from the drive and can cause Longer load times that look like Kontakt is not responding.
This will only be a problem in larger libraries with big .nki files. What happens is Kontakt has to scan the folder you have selected and find every sample, which is not an issue for most libraries but for libraries that use a lot of samples in a single .nki file you can run into some issues if the drive is not optimized for Kontakt.
The most efficient format for Mac Users is Mac OS (Journaled). The most efficient format for Windows users is NTFS.
We also recommend that you check our guide on Kontakt Optimization. Following the steps in this guide can also help prevent a library from hanging.