Problem with borderlayout south/center inside tab panel

<tabpanels>
	<tabpanel id="panelScenarioProps" width="100%" height="100%">
		<borderlayout height="100%" width="100%">
			<center>
				<grid width="100%" height="100%">
					<columns>
						<column width="140px"
							label="" />
						<column label="" />
					</columns>
					<rows>
						<row>
							<label value="New scenario name" />
							<textbox value="@load(vm.newScenarioTitle) @save(vm.newScenarioTitle, before='propsNext')"
													cols="100" constraint="no empty" />
						</row>
						<row>
							<label value="Description" />
							<ckeditor value="@load(vm.newScenarioDesc) @save(vm.newScenarioDesc,before='propsNext')"
													toolbar="Basic" height="150px" />
							<label /								</row>
						<row								<label value="Source" />
							<hlayout>
							<radiogroup onCheck="sourceScenarios.setDisabled(sourceNew.isChecked());">
								<radio id="sourceNew" label="New" checked="@load(vm.sourceNew) @save(vm.sourceNew,before='propsNext')" />
								<radio
															label="Derived"
															checked="@load(vm.sourceDerived) @save(vm.sourceDerived,before='propsNext')" />
								</radiogroup>
								<combobox
														id="sourceScenarios"
														value="@load(vm.selectedSourceScenario) @save(vm.selectedSourceScenario,before='propsNext')"
														model="@load(vm.sourceScenarios)"
														disabled="@load(vm.sourceNew)" readonly="true"
														selectedItem="@bind(vm.selectedSourceItem)">
									<template
															name="model" var="option">
									<comboitem
																label="@bind(option.title)" />
								</template>
													</combobox>
							</hlayout>
						</row>
					</rows>
				</grid>
			</center>
			<south height="50px">
				<grid width="100%">
					<columns>
					<column width="140px" label="" />
						<column label="" />
					</columns>
					<rows>
						<row>
							<space />
							<hlayout>
								<button label="Cancel" onClick="@command('propsCancel')" />
								<space />
								<button label="Next"
														onClick="@command('propsNext')" />
							</hlayout>
						</row>
					</rows>
				</grid>

			</south>
		</borderlayout>

	</tabpanel>