You can't use the first few feet of heat cable to "heat" anything. I keep reading about people who's bottom tubs are too cold and others saying it's because too close to the floor. I wonder if people have not accounted for the cold lead and have heat cord under the bottom bin that isn't heated. I have a few different lengths/watts of Zoo Med heat cable. One says it has 2 feet of cold lead, the other says it has 6.5 feet of cold lead. If you still have your box and instructions look to see how many feet of cold lead you have then be sure you have at least that much free cord hanging out. Or you can wait till the thermostat kicks the heat cable on and try to feel for where the heated part ends to be sure you have all hot cable under the bottom bin and none of the cold lead. Unfortunately they don't mark on the heat cable where the cold lead ends... wish they did. If you can increase your room temp so that your cold sides are warmer that would help too. And like the other poster said, if it just can't be resolved, don't use that bin for housing, use it to hold snakes temporarily while you are cleaning their tubs or something.
.

-----
Slytherin Serpents
Have you been hugged by your snake today? 
Ball Pythons
1.1 Het Caramels (Edward & Bella)
0.1 Normal 66% ph Caramel (Rosalie)
1.1 Caramels (Crookshanks & Bellatrix)
1.0 Honey Bee (Aragog)
0.1 Hypo Pastel (Nagini)
0.1 Spider 66% ph Hypo(Nymphadora)
1.0 Mojave (Lucius)
1.1 Pastel Lessers (Jacob & Narcissa)
0.1 Pinstripe (Arwen)
1.0 Pewter (Salazar)
0.1 Bumble Bee (Alice)
1.0 Bell Pastel (Jasper)
0.1 African Dinker (Esme)
0.1 Het Pied
0.1 Hypo Cinny (Myrtle)
1.0 Cinny het Hypo poss het Albino
1.1 Pastel Dinkers (Snape & Xiomara)
0.2 Ghana Dinker Babies
0.0.3 CH Dinker Babies
Corns
1.1 Normals het Amel, Anery, Charcoal, Diffused, Hypo (Romeo & Juliet)
1.0 Blizzard het Diffused (Tumnus)
1.0 Blizzard poss het Anery, Hypo, Diffused (Cotton)
0.1 Anery Lavender het Amel (Lucy)
0.1 Plasma poss het Hypo (Victoria)
1.0 Plasma poss het Albino
1.0 Hypo Plasma
1.1 Amel Motleys (Harry & Ginny)
0.1 Lavender Motley poss het diffused
1.0 Lavender Pinstripe Motley het Amel
0.1 Fire poss het Anery, Charcoal, Hypo (LeeLoo)
0.1 Normal het Albino, Lavender, Anery, Charcoal, poss het Diffused
1.0 Albino het Lavender, Anery, Charcoal, poss het Diffused
1.1 Sunkissed poss het Plasma (Arthur & Molly)
0.1 Dilute Blue Motley (Myrtle)
1.0 Pastel Motley (Nick)
0.1 Diffused Caramel
1.0 Blizzard 66% poss het Diffused
1.0 Pewter het Albino
0.1 Fire het Charcoal
Thayeri Kings
0.1 Leonis phase (Sidney)
1.0 Milk Snake phase
Milks
1.1 Tangerine Albino Hondurans
0.1 Hypo Tangerine Albino Honduran