Vending Machine not recognising skinned items

When attempting to sell sunglasses, certain skins are not counted toward the quantity of the vending machine.

Example 1
Given the following contents of a vending machine:

The quantity showing on the map:

Which means that two sunglasses aren't recognised.

Example 2
Given the following contents of a vending machine:

Shows as "Out of stock" on the map:

There is no discernable difference between the two types of sunglasses.

The output of find_radius 2 from console results in:

realm entity  group parent  name                   position             local                rotation             local                 status invokes 

cl    82971   33905 0       player                 (-4.9, 17.6, -493.3) (-4.9, 17.6, -493.3) (0.0, 81.4, 0.0)     (0.0, 81.4, 0.0)                     

cl    3176455 33905 0       foundation             (-6.2, 17.4, -493.1) (-6.2, 17.4, -493.1) (0.0, 272.7, 0.0)    (0.0, 272.7, 0.0)                    

cl    2901370 33905 2883052 lasersight.entity      (-5.1, 18.3, -493.6) (0.0, 0.0, 0.0)      (68.1, 115.7, 19.1)  (0.0, 0.0, 0.0)       child          

cl    3296976 33905 82971   planner                (-5.3, 18.5, -493.6) (0.0, 0.0, 0.0)      (351.1, 237.4, 87.4) (0.0, 0.0, 0.0)       child          

cl    2883052 33905 82971   pistol_semiauto.entity (-5.2, 18.5, -493.5) (0.0, 0.0, -0.1)     (8.5, 269.0, 74.9)   (283.8, 164.4, 192.7) child          

cl    2807118 33905 82971   planner                (-5.3, 18.5, -493.6) (0.0, 0.0, 0.0)      (351.1, 237.4, 87.4) (0.0, 0.0, 0.0)       child          

cl    2690041 33905 82971   hammer.entity          (-5.3, 18.5, -493.6) (0.0, 0.0, 0.0)      (351.1, 237.4, 87.4) (0.0, 0.0, 0.0)       child          

cl    3305450 33905 82971   planner                (-5.3, 18.5, -493.6) (0.0, 0.0, 0.0)      (351.1, 237.4, 87.4) (0.0, 0.0, 0.0)       child          

cl    3301104 33905 82971   planner                (-5.3, 18.5, -493.6) (0.0, 0.0, 0.0)      (351.1, 237.4, 87.4) (0.0, 0.0, 0.0)       child          

cl    3299907 33905 82971   planner                (-5.3, 18.5, -493.6) (0.0, 0.0, 0.0)      (351.1, 237.4, 87.4) (0.0, 0.0, 0.0)       child          

cl    3298872 33905 82971   planner                (-5.3, 18.5, -493.6) (0.0, 0.0, 0.0)      (351.1, 237.4, 87.4) (0.0, 0.0, 0.0)       child          

cl    149023  33905 82971   mace.entity            (-5.3, 18.5, -493.6) (0.0, 0.0, 0.0)      (351.1, 237.4, 87.4) (0.0, 0.0, 0.0)       child          

cl    617833  33905 82971   chainsaw.entity        (-5.3, 18.4, -493.2) (0.3, 0.0, 0.2)      (9.0, 20.8, 259.3)   (342.1, 0.0, 7.5)     child          

cl    130895  33905 82971   knife_bone.entity      (-5.3, 18.5, -493.6) (0.0, 0.0, 0.0)      (351.1, 237.4, 87.4) (0.0, 0.0, 0.0)       child          

cl    3176416 33905 0       foundation             (-3.2, 17.4, -493.2) (-3.2, 17.4, -493.2) (0.0, 272.7, 0.0)    (0.0, 272.7, 0.0)                    

cl    3177255 33905 0       wall                   (-6.2, 17.4, -494.6) (-6.2, 17.4, -494.6) (0.0, 92.7, 0.0)     (0.0, 92.7, 0.0)                     

At the time I had 4 pairs of sunglasses on me, and only one building planner.