TYPO3 Core

Our mediaType field is a selectSingle with two values.
While Updating TYPO3 from 9 to 11 we came across this issue.

We updated the field type from "select" to "selectSingle" but the translations are not being rendered if I switch the type to "check" just for fun the output of the options are correctly translated.

The given XLF File and Key are correct or else even the type "check" wouldn't work.

<mediaType>
<TCEforms>
<label>Type</label>
<description>LLL:EXT:frp_template/Resources/Private/Language/locallang_db.xlf:tt_content.frptemplate_hero.pi_flexform.media.description</description>
<onChange>reload</onChange>
<config>
<type>selectSingle</type>
<items type="array">
<numIndex index="0" type="array">
<numIndex index="0">LLL:EXT:frp_template/Resources/Private/Language/locallang_db.xlf:tt_content.frptemplate_hero.pi_flexform.slider</numIndex>
<numIndex index="1">slider</numIndex>
</numIndex>
<numIndex index="1" type="array">
<numIndex index="0">LLL:EXT:frp_template/Resources/Private/Language/locallang_db.xlf:tt_content.frptemplate_hero.pi_flexform.video</numIndex>
<numIndex index="1">video</numIndex>
</numIndex>
</items>
<default>slider</default>
</config>
</TCEforms>
</mediaType>