Operand data type bit is invalid for max operator.

​@John Kihiu This is a known compatibility issue that surfaces after Acumatica upgrades. Here's a full breakdown: 
This is a SQL Server error, not an Acumatica application error. It occurs when Acumatica's  customization tries to execute something like: 

SELECT MAX(MyBooleanField) FROM MyTable

-- SQL Server does NOT support MAX() on a BIT column
-- This is a SQL Server limitation, not Acumatica's

 Solution:

DAC Change

// BEFORE 
[PXDBBool]
[PXUIField(DisplayName = "My Flag")]
public virtual bool? MyFlag { get; set; }

// AFTER 
[PXDBInt]
[PXUIField(DisplayName = "My Flag")]
public virtual int? MyFlagInt { get; set; }

// Keep bool property for UI convenience
public virtual bool? MyFlag
{
    get { return MyFlagInt == 1; }
    set { MyFlagInt = value == true ? 1 : 0; }
}

Database Column Change (Most Thorough)

-- Change BIT column to INT in the database
ALTER TABLE [MyCustomTable] 
ALTER COLUMN [MyBooleanField] INT NOT NULL DEFAULT 0;

-- Update existing values
UPDATE [MyCustomTable] 
SET [MyBooleanField] = CASE 
    WHEN [MyBooleanField] = 1 THEN 1 
    ELSE 0 
END;