Test for button press every 50ms. That's more than enough.

include/controller.h

@@ -14,6 +14,7 @@ class Controller {
 	Playlist current_playlist;
 	bool is_rfid_present = false;
 	unsigned long last_rfid_check = 0;
+	unsigned long last_button_check = 0;
 	uint8_t button_pressed = 0;
 	unsigned long button_pressed_since = 0;
 	bool button_already_processed = false;