Unexpected Error on Custom Forms

Steps to Reproduce:
A. Create a custom record type:
1. Navigate to Customization > Lists, Records, & Fields > Record Types > New.
2. Enter a Name. (Ex. Merchant Brand)
3. Save.
4. Click the New Field button on the Fields tab.
5. Enter a name in the Label field. (Ex. Category)
6. Set Type to List/Record.
7. Select a value in the List/Record field.
8. Save.

B. Create Custom Entity Field 1:
1. Navigate to Customization > Lists, Records, & Fields > Entity Fields > New.
2. Enter a name in the Label field. (Ex. Category)
3. Set Type to List/Record.
4. Select a value in the List/Record field. (value should be the same as the value of the List/Record field in the Category field of the custom record type in step A).
5. Check the Customer check box on the Applies To tab.
6. Save.

B. Create Custom Entity Field 2:
1. Navigate to Customization > Lists, Records, & Fields > Entity Fields > New.
2. Enter a name in the Label field. (Ex. Brand)
3. Set Type to List/Record.
4. Select Merchant Brand in the List/Record field.
5. Check the Customer check box on the Applies To tab.
6. Click Sourcing & Filtering tab.
7. Select Category in the Filter Using column.
8. Leave Compare Type to equal.
9. Select Category in the Compare to Field column.
10. Save & Apply to Forms.
11. Edit the field.
12. Check the Show checkbox for your custom form.
13. Save.

C. Edit the Category field of the custom record type.
1. Navigate to Customization > Lists, Records, & Fields > Record Types.
2. Click Merchant Brand.
3. Click Category on the Fields tab.
4. Change the Type to Multiple Select.
5. Save.

D. Navigate to Lists > Relationships > New.

Result: Unexpected error.

Solution:
The Type of the field being compared (Category customer field and Category field on custom record) on custom Brand entity field should be the same.