So I'm designing this canard delta wing fighter aircraft heavily inspired by the F/A-18 Hornet, and at one point, I got it to perform exceptionally well (balance was good and pitch/roll authority was stable and excellent), hence I decided to take a break. It was when I got back from this hiatus that things went sideways; when I resumed with the project—I noticed that the plane bobs when I pitch up or down then let go of the stick, and to make things worse, I can't remember what I changed for it to behave this way. But I knew this had something to do with the control surface deflection and stall characteristics. So, I tried my best to make adjustments while keeping these into account: I tried shifting the balance, CoM and CoF placement, tweaking the canard shape and size, etc. but nothing worked.

Here's a link to the aircraft if any of you wanna check it out.
https://www.simpleplanes.com/a/bvXvqU/Test-Aircraft-WIP (I'm on mobile btw).

Any help, suggestions, or insight would be much appreciated. (Also, pls excuse my english. It's not my first language)