Two m.Slider controls, same properties, yet one doesn't show the marks - sapui5

Question

enableTickmarksis true for both slider controls, yet only one shows them?
<core:FragmentDefinition xmlns="sap.m" xmlns:core="sap.ui.core">
<Dialog title="{Title}" icon="sap-icon://create">
<beginButton>
<Button text="{i18n>cancel}" press="handleCloseCompetencySelection"/>
</beginButton>
<endButton>
<Button type="Accept" text="{i18n>submit}" press="handleSubmitCompetencySelection"/>
</endButton>
<content>
<FlexBox direction="Column" alignItems="Center" class="sapUiMediumMarginTopBottom">
<items>
<HBox><Label text="{i18n>required}: "/><Label id="RequiredProficiencyLabel" text="{ProfidrDescr}" design="Bold"/></HBox>
<Slider id="RequiredProficiencySlider" enabled="false" liveChange="onSliderChange" enableTickmarks="true" min="0" max="10"
class="sapUiSmallMarginBottom" width="400px"/>
</items>
</FlexBox>
<FlexBox direction="Column" alignItems="Center" class="sapUiMediumMarginTopBottom">
<items>
<HBox><Label text="{i18n>achieved}: "/><Label id="ProficiencyLabel" text="" design="Bold"/></HBox>
<Slider id="ProficiencySlider" liveChange="onSliderChange" enableTickmarks="true" min="0" max="10" class="sapUiSmallMarginBottom"
width="400px"/>
</items>
</FlexBox>
<MessageStrip text="{i18n>dragMessage}" type="Information" showIcon="true" class="sapUiMediumMargin"></MessageStrip>
</content>
</Dialog>
</core:FragmentDefinition>

Answer 1

There was a bug which is fixed as of version 1.52. The z-index of tickmarks was incorrectly set. Here you can see that the tickmarks are displayed correctly in Dialog: https://jsbin.com/ruqosej/edit?html,js,output

Answer 2

Funny story:
for "disabled" slider that tickmark looks bolder and perceptible than "enabled" one
the second slider shows the tickmarks, but you are not able to see them due to the very light grayscale color of the marks (to make sure that it is true, try to look at the sceen with different angle and you will see the tickmarks of the second slider; or use another display)