Conflict control ID

I am having problem in publishing my custom project in Acumatica ERP. It prompts me the following message.

Conflict control ID:phG_tab_Items#0_grid_Levels#0 from page ~/pages/so/so303000.aspx Validation failed.

Here is what my code looks like in the Invoices page (ScreenID: SO303000)

<Page path="~/pages/so/so303000.aspx" ControlId="2" pageSource="711Ft7m6F+foDk0z4+/8B">
    <PXGridLevel DataMember="Transactions" ParentId="phG_tab_Items#0_grid_Levels#0" TypeFullName="PX.Web.UI.PXGridLevel">
        <Children Key="Columns">
            <AddItem>
                <PXGridColumn TypeFullName="PX.Web.UI.PXGridColumn">
                    <Prop Key="DataField" Value="UsrContractID" />
                    <Prop Key="Width" Value="70" />
                </PXGridColumn>
            </AddItem>
            <AddItem>
                <PXGridColumn TypeFullName="PX.Web.UI.PXGridColumn">
                    <Prop Key="DataField" Value="UsrPhoneNumber" />
                    <Prop Key="Width" Value="70" />
                </PXGridColumn>
            </AddItem>
            <AddItem>
                <PXGridColumn TypeFullName="PX.Web.UI.PXGridColumn">
                    <Prop Key="DataField" Value="UsrSIMCardID" />
                    <Prop Key="Width" Value="160" />
                </PXGridColumn>
            </AddItem>
        </Children>
    </PXGridLevel>
</Page>

I have shortened the pageSource value for readability.

Since, I have another custom project as well, and got answer that that could cause this, I have no idea what changes should I do to make this work.

Solution

When you publish more that one customization project, the system merges the content of all projects into a single customization project. If different projects include customization for the same ASPX page, the platform tries to merge the changes. For example, the platform can merge different properties of the same control in an ASPX page.

On the Customization Projects form, you can specify an optional number (level) for each customization project, assigning the highest number to the most important change. The level can be used to resolve conflicts that arise while you are publishing customization projects if multiple modifications for the same ASPX page are merged. As a result, the customization from the project with the highest level is added to the merged project.

For more information on this topic, please check Acumatica Customization Guide