How to make iFile not cache .plist files after updating to iOS 8?
It's not iFile caching the property lists, it's iOS 8 doing this. For improved performance, preference files are not actually read from file often—only when necessary. Furthermore, the cache that iOS maintains can overwrite the stored property list files when necessary, meaning that it can be difficult to change preferences. SyncedPreferences also adds to the complexity, being that iCloud must update the key-value pair asynchronously with the iOS 8 cache. As far as I am aware, there is no way round this other than changing the property list when the app is guaranteed to not be storing its preferences in cache (i.e. just after a reboot).