Expected behavior

I have a struts 2 page with 2 selects, one of them should be searchable. They both are using the s:select option, which generates a standard HTML select. I expect both selects to work properly, with the first select to be a basic select and the second select to have a search.

Actual behavior

The first select gets the search functionality the second select should have. The second select has the input field rendered but doesn't do anything when clicked.

Resources (screenshots, code snippets etc.)

Source Code:

<%--                    'LevelOid' Select --%>
<div class="row mb-3">
    <label for="select" class="col-lg-3 col-form-label">Basic
        Select</label>
    <div class="col-lg-9">
        <div class="d-flex mx-5">
            <div class="w-100">
                <s:select id="select" data-mdb-select-init="" name="select"
                    theme="simple" list="selectOptions" listKey="id"
                    listValue="name" />
            </div>
            <span class="c-table-basic__required">*</span>
        </div>
    </div>
</div>
<%--                    'LevelOid' Select --%>
<div class="row mb-3">
    <label for="filteringSelect" class="col-lg-3 col-form-label">Filtering
        Select</label>
    <div class="col-lg-9">
        <div class="d-flex mx-5">
            <div class="w-100">
                <s:select id="filteringSelect" data-mdb-select-init="" name="filteringSelect"
                    data-mdb-filter="true" theme="simple" list="selectOptions"
                    listKey="id" listValue="name" />
            </div>
            <span class="c-table-basic__required">*</span>
        </div>
    </div>
</div>

Actual behavior: