Your problem may be related to Grid reconstruction and how to avoid it FAQ #8019

>The error "Unknown member GRCWAREHOUSE" appears when the form Init() hits. The error is intermittent and we don't know what else to look for.
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>Here's the background:
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>The form has 3 grids in it. The error occurs in the form.init() where assignment of the record source and control source occurs. We have verified that the record source exists. Record source assignment is successful so it meant that the grid object exists. Control source assignment fails returning the error message. GRCWAREHOUSE is the name of the column in the grid (as opposed to the default COLUMN1). Coding looks like this:
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>with .EgrdItemWhs
>   .RecordSource = "CurWhs1"
>   .GrcWarehouse.ControlSource = "CurWhs1.cWarehouse"
>endwith
>

>
>Any idea will be appreciated.