I did test each of the screws that couldn't fit into this unit's top rails by screwing them into holes in at least two other racks or rack-cases, and in every case, the screws that could not be used with this rack/stand worked perfectly in every hole of every other rack I tested them with

So, the screws are just fine

And yet, no matter how much I torque down the two knobs as well as the 2 screws at the pivot point of the top slanted portion, it refuses to go down in its lower position (most slanted to the front direction), instead insisting on moving into a more flat position although not completely flat