Perfect, thank MB Themes.
I solved it in the following way:
in file item-post.php make the following changes:
replace line 54
<form name="item" action="<?php echo osc_base_url(true);?>" method="post" enctype="multipart/form-data" id="item-post">
for
<form name="item" action="<?php echo osc_base_url(true);?>" method="post" enctype="multipart/form-data" id="item-post" onsubmit="return disableButton()">
replace line 259
<button type="submit" class="btn btn-primary pbl"><?php if($edit) { _e("Update", 'sigma'); } else { _e("Publish", 'sigma'); } ?></button>
for
<button id="submitButton" type="submit" class="btn btn-primary pbl"><?php if($edit) { _e("Update", 'sigma'); } else { _e("Publish", 'sigma'); } ?></button>
and add end file
<script>
function disableButton() {
document.getElementById("submitButton").disabled = true;
return true; // Devuelve true para permitir que el formulario se envĂe
}
</script>