Debounce slide switches in verilog?
I doubt you have issue in your Verilog code , and you say that weird behavior.
The  oscilloscope images seems normal.
Try this simple example :

Switches to LEDs

`timescale 1ns / 1ps

module top(
    input [3:0] switches,
    output [3:0] leds
    );
    
    assign leds = switches;
endmodule

Remember to add constraint file for the switches and LEDs.
Still if you need to debounce switches,  The easiest way to debounce switches / Push buttons in Verilog is to use  Slow clock.
In order to achieve a slow clock , you have to use a clock divider , divide your 16MHz clock into something slower like 8MHz or 4MHz. With a slower clock you'll be able to catch the event.
Read this Article