KONTAKT is taking a very long time to load a library or to change presets.
A Batch Re-save will resave your KONTAKT Instrument Files with sample path information specific for your system. This can help reduce the loading time of an instrument significantly. This article explains how to do this.
Antivirus and Backup Software
In some cases, the problem could be occurring due to antivirus software or the 'active monitoring' of a backup software preventing KONTAKT from operating properly. Please temporarily disable these programs while using KONTAKT or create exclusions for your KONTAKT library folders in your antivirus software.
For macOS, it is recommended to use the format HFS+ / Mac OS Extended (Journaled) on macOS 10.12 and earlier. On macOS 10.13 and later, Apple File System (APFS) is recommended. These are the standard disk formats.
For Windows systems, it is recommended to use the NTFS format. That is the standard disk format on Windows computers.