TCA (flexform) multi select - typo3

Question

I work on an extension and for a plugin I want to select specific records. For that I created a flexform with a TCA select configuration:
<T3DataStructure>
<meta>
<langDisable>1</langDisable>
</meta>
<sheets>
<sDEF>
<ROOT>
<TCEforms>
<sheetTitle>TEST</sheetTitle>
</TCEforms>
<type>array</type>
<el>
<settings.selection>
<TCEforms>
<exclude>1</exclude>
<label>Selection</label>
<config>
<type>select</type>
<foreign_table>tx_mycollection_domain_model_mycollection</foreign_table>
<renderType>selectCheckBox</renderType>
<size>5</size>
<minItems>3</minItems>
<maxItems>999</maxItems>
<foreign_table_where>AND tx_mycollection_domain_model_mycollection.sys_language_uid=###REC_FIELD_sys_language_uid###</foreign_table_where>
</config>
</TCEforms>
</settings.selection>
</el>
</ROOT>
</sDEF>
</sheets>
</T3DataStructure>
It looks fine, in the backend I have checkboxes to select the records. But when I save the plugin only the first checkbox is checked/saved.
Is there something wrong in the configuration or what could be the reason that I can not save multible values?

Answer 1

<minItems>3</minItems>
<maxItems>999</maxItems>
From the documentation here:
https://docs.typo3.org/typo3cms/TCAReference/Reference/Columns/Select/Index.html#properties
These needs to be specified as all lower case, so changing them to:
<minitems>3</minitems>
<maxitems>999</maxitems>
Should resolve your issue. It is saving only 1 right now, since maxitems by default is set to 1.