IT is firmware issue. Present in other ROMs alsoI was sure about it.
Maybe it's because of how the screen lights up after the fingerprint is authorized.
Look closely, after touching the fingerprint, the hardware buttons light up first, then the main screen turns on, if we can reduce the time of screen turning on, or make the screen to light up, as soon as the Hardware buttons light up. Maybe then we will find the FP unlock to be fast.
Or, it is a Firmware problem.
Please, Dev @xyyx have a look into it.
Status Bar: - Network traffic; - Bluetooth device battery level in status bar; - Adjust brightness by sliding across the status bar; - Input method selector notification. Quick Settings: - Number of rows and columns; - Quick pulldown; - No QS on secured lockscreen; - Brightness slider; - Smart pulldown; - Show/hide adaptive brightness icon in QS; - LTE enable/disable tile. - Hiding tile's caption Buttons: For devices with hardware buttons - Enable/disable buttons; - Adjust brightness; - Keys brightness timeout; - Reassignment hardware buttons action; - Volume rocker wake; - Playback control by volume keys; - Allow volume keys to enable/disable “Do Not Disturb” mode. Navigation Bar: - 3 type navigation bar mode: Smartbar (as usual in android) and Fling (navbar from “Dirty Unicorns” rom), AOSP Navbar; - Pulse settings in Fling navbar; - Navbar height control in portrait and landscape orientations; - Context buttons layout position; - Context buttons transparency; - Button touch animation; - Cursor arrows in navbar while typing; - Force show/hide navbar on the bottom side when device is rotated; Gestures: - Open camera by double tap the power button; - Double tap on lockscreen to put the device to sleep; - Double tap status bar to put the device to sleep; Lock Screen: - Lock screen shortcuts; - Show/hide weather on lock screen; - Longpress power button with lock screen turn on torch; Power Menu: - Customizing power menu; - Enable/disable power menu on secure lock screen. Recents apps: - Exclude apps from the recents panel; - Select recents view. - Clear all button positions Miscellaneous: - Screenshot type – fullscreen screenshots or selected area as a screenshots; - Enable MTP instead charging after connect to PC; - Wakelock blocker; - Alarm blocker - App ops; - Wake up device if charger is plugged/unplugged; - Allow signature spoofing (microG). Other: - Quick unlock - Enable/disable dashboard suggestions, conditions;