Custom selector field working in one tenant, but errors in second tenant

Changed approach and used a different method to define the Item Class. Instead of using a constant in the code, created a custom checkbox on the Item Class, to flag it as the relevant class for the selector to show items of that class.

Item Class DAC Extension:

public class INItemClassExt : PXCacheExtension<PX.Objects.IN.INItemClass>
{
  #region CustomItemClassFlag
  [PXDBBool]
  [PXUIField(DisplayName="Custom Item Class Flag")]
  public virtual Boolean? CustomItemClassFlag { get; set; }
  public abstract class customItemClassFlag : PX.Data.BQL.BqlBool.Field<customItemClassFlag> { }
  #endregion
)

Purchase Order DAC Extension:

public class POOrderExt : PXCacheExtension<PX.Objects.PO.POOrder>
{

  #region CustomField
  [PXDBString(50)]
  [PXUIField(DisplayName = "Custom Field")]
  [PXSelector(
      typeof(Search2<InventoryItem.inventoryCD,
          InnerJoin<INItemClass, On<InventoryItem.itemClassID, Equal<INItemClass.itemClassID>>>,
          Where<INItemClassExt.customItemClassFlag, Equal<True>>>),
      typeof(InventoryItem.inventoryCD),
      typeof(InventoryItem.descr),
      SubstituteKey = typeof(InventoryItem.inventoryCD),
      DescriptionField = typeof(InventoryItem.descr))]
  public string CustomField { get; set; }
  public abstract class customField : IBqlField { }
  #endregion
)