提交留言的时候会显示这个，再次提交才能成功，是哪个环节出现了问题？？
留言代码如下：
{eyou:form type='default' formid='3' id='field'}
<form action="{$field.action}" {$field.formhidden} method="post" on-submit="{$field.submit}" class="appointment-form">
<div class="form-grid">
<div class="form-group">
<label class="form-label">
<span class="required">*</span>姓名
</label>
<input type='text' id='attr_50' class="form-input" placeholder="请输入您的真实姓名" name='{$field.attr_50}'>
</div>
<div class="form-group">
<label class="form-label">
<span class="required">*</span>手机号
</label>
<input type='text' id='attr_51' name='{$field.attr_51}' class="form-input" placeholder="请输入11位手机号码">
</div>
<div class="form-group">
<label class="form-label">
<span class="required">*</span>微信号
</label>
<input type='text' id='attr_52' name='{$field.attr_52}' class="form-input" placeholder="请输入您的微信号">
</div>
<div class="form-group">
<label class="form-label">
<span class="required">*</span>学制
</label>
<select name='{$field.attr_53}' id='attr_53' class="form-select">
<option value='无'>请选择学制</option>
{eyou:volist name='$field.options_53' id='vo'}
<option value='{$vo.value}'>{$vo.value}</option>
{/eyou:volist}
</select>
</div>
<div class="form-group">
<label class="form-label">
<span class="required">*</span>意向专业
</label>
<select name='{$field.attr_54}' id='attr_54' class="form-select">
<option value='无'>请选择专业</option>
{eyou:volist name='$field.options_54' id='vo'}
<option value='{$vo.value}'>{$vo.value}</option>
{/eyou:volist}
</select>
</div>
<div class="form-group">
<label class="form-label">
沟通方式
</label>
<select name='{$field.attr_55}' id='attr_55' class="form-select">
<option value='微信'>请选择沟通方式（默认微信）</option>
{eyou:volist name='$field.options_55' id='vo'}
<option value='{$vo.value}'>{$vo.value}</option>
{/eyou:volist}
</select>
</div>
</div>
<div class="form-actions">
<input type="submit" class="btn-submit" value="提交预约">
</div>
<div class="form-tips">
<h4><i class="fas fa-lightbulb"></i> 温馨提示</h4>
<ul>
<li>预约成功后，老师将在24小时内与您联系</li>
<li>请保持手机/微信畅通，以便接收相关通知</li>
</ul>
</div>
{$field.hidden}
</form>
{/eyou:form}