A question about your verilog files

[fhrgithub]

Dear author,
I ran your program and your Matlab program runs very well.
But there seems to be something wrong with the verilog program.
I tested two tb files separately but the results were unexpected.

The frequency in the figure above is 2K.

The frequency in the figure above is 6K.
The verilog program doesn't seem to be working properly.

Could you give me some help?Look forward to your reply.