KDE桌面效果配置按钮点击后出现Could not locate package metadata错误求助

我正在开发一款KWin桌面特效的配置菜单，点击配置按钮后并未弹出配置UI，而是出现错误提示：

Could not locate package metadata

以下是我的项目目录结构、UI文件、配置文件及元数据文件：

目录结构 #

kwin4_effects_foldpopups
├── contents
│   ├── code
│   │   └── main.js
│   ├── config
│   │   └── main.xml
│   └── ui
│       └── config.ui
└── metadata.json

ui/config.ui #

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>FoldPopupsEffectConfig</class>
 <widget class="QWidget" name="FoldPopupsEffectConfig">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>338</width>
    <height>89</height>
   </rect>
  </property>
  <property name="sizePolicy">
   <sizepolicy hsizetype="Preferred" vsizetype="Preferred">
    <horstretch>0</horstretch>
    <verstretch>0</verstretch>
   </sizepolicy>
  </property>
  <property name="windowTitle">
   <string>Fold Popups Effect Configuration</string>
  </property>
  <layout class="QGridLayout" name="grid_layout">
   <item row="0" column="0">
    <widget class="QLabel" name="duration_label">
     <property name="text">
      <string>Animation Duration</string>
     </property>
     <property name="alignment">
      <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
     </property>
    </widget>
   </item>
   <item row="0" column="1">
    <widget class="QSpinBox" name="kcfg_Duration">
     <property name="suffix">
      <string> milliseconds</string>
     </property>
     <property name="minimum">
      <number>300</number>
     </property>
     <property name="maximum">
      <number>5000</number>
     </property>
     <property name="singleStep">
      <number>10</number>
     </property>
    </widget>
   </item>
   <item row="1" column="0">
    <widget class="QLabel" name="behavior_label">
     <property name="text">
      <string>Animation Behavior</string>
     </property>
     <property name="alignment">
      <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
     </property>
    </widget>
   </item>
   <item row="1" column="1">
    <widget class="QLabel" name="tbc_label">
     <property name="text">
      <string>To be continued</string ><!-- TODO: Add behaviour options here -->
     </property>
     <property name="alignment">
      <set>Qt::AlignLeading|Qt::AlignLeft|Qt::AlignVCenter</set>
     </property>
    </widget>
   </item>
  </layout>
 </widget>
 <resources/>
 <connections/>
</ui>

config/main.xml #

<?xml version="1.0" encoding="UTF-8"?>
<kcfg xmlns="http://www.kde.org/standards/kcfg/1.0"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://www.kde.org/standards/kcfg/1.0 http://www.kde.org/standards/kcfg/1.0/kcfg.xsd">
  <kcfgfile name=""/>
  <group name="">
    <entry name="Duration" type="UInt">
      <default>300</default>
    </entry>
  </group>
</kcfg>

metadata.json #

{
    "KPackageStructure": "KWin/Effect",
    "KPlugin": {
        "Name": "Fold Popups",
        "Name[zh_CN]": "气泡折叠动画",
        "Description": "Make popups smoothly fold in and out when they are shown or hidden",
        "Comment[zh_CN]": "气泡信息显示/隐藏时呈现折叠过渡动画",
        "Category": "Appearance",
        "Authors": [
            {
                "Email": "kde-yyds@qq.com",
                "Name": "kde-yyds"
            }
        ],
        "Icon": "preferences-system-windows-effect-fadingpopups",
        "Id": "kwin4_effects_foldpopups",
        "License": "GPL",
        "Version": "1.0",
        "EnabledByDefault": "true",
        "ServiceTypes": ["KWin/Effect"]
    },
    "Type": "Service",
    "X-KDE-Ordering": "60",
    "X-KDE-PluginKeyword": "kwin4_effects_foldpopups",
    "X-KDE-ConfigModule": "kwin/effects/configs/kcm_kwin4_genericscripted",
    "X-KWin-Config-TranslationDomain": "kwin_effects",
    "X-Plasma-API": "javascript",
    "X-Plasma-MainScript": "code/main.js",
    "X-KDE-ParentApp": "kwin"
}

我已经查阅过相关文档，按照规范配置了文件，也参考过其他能正常显示配置菜单的特效元数据进行修改，但问题依旧。我注意到其他特效如果Id参数和目录名称不一致时会出现相同错误，但我的Id和特效目录名称完全一致，还是报错，求解决办法。

内容的提问来源于stack exchange，提问作者DolphyWind