Horizontal Striations on Models

I’m currently experiencing a great deal of issues with my new Flashforge Finder. At some point, my printer managed to become unleveled and gouge the buildplate. This has managed to spiral into a larger problem: horizontal striations on any model I try to print. I have replaced the nozzle and the build plate, re-leveled countless times (though I feel it isn’t leveling properly), looked for clogs or broken pieces of metal in the extruder/motor, and greased the horizontal/vertical rods.

I’ve also tried running models slower and with varying temperatures to achieve different results, though previous to this I never had problems producing models with factory defaults. Therefore I’m feeling like it’s not speed or temperature that is the problem. Perhaps it is vibrations or the extruder being loose? (Though I’ve tightened all the bolts, etc. as much as possible…)

I’m honestly at a loss as to what to do. I’ve included photos of a successful model from before making repairs and a more recent model. IMG_7016IMG_6985 IMG_7018

What might be the problem causing these striations and printing errors?

EDIT: While trying to replace the nozzle, I had to remove the heating element. To do this, I had to remove many bolts/threaded connections. One which keeps the heating element firmly attached to the print head, which practically has no head and which is not clearly shown in FlashForge’s videos, was not replaced properly; I’m hoping this has made the vibrations and caused the ripple effect. If anyone has a similar problem, I’d check to be sure this practically microscopic connection is made!