DF 19.1

When I click F4 to call a cWebPromptList with a list of products in a web order application, the cWebPromptList shows but doesn't take the focus. The cursor stays behind in the cWebGrid. If I click Up or Down arrow, the cursor doesn't move inside my cWebPromptList, but behind in the cWebGrid.
If I click any line in the cWebPromptList then it takes the focus. I hope I explained myself.

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How can I solve this? I though it was a DF_Material theme problem, but I have tried with DF_Flat_Desktop and it happens there too.