Change Parent Item Class - unable to see total list of available item classes

Summary

Cannot see total item class list to select from

Content

Hello, 

I want to change the Parent Item Class, but I do not see all created Item Classes as options when selecting certain item classes in the hierarchy. 

For example: 

When I select Finish Goods_test_3 --> Actions --> Change Parent Item Class I am able to see a larger list of item classes to change to. 

When I select FG_Test_4 --> Actions --> Change Parent Item Class I am not able to see the available item classes to change to. I only see FG_Test_4 and its sibling in the class, V3_FGA_test.