如何解决错误：使用一键导入WordPress导入数据时，内部服务器错误(500)？

我正在从事WordPress主题开发, 一键演示导入时出现错误。我增加了最大执行时间, 但仍然收到此错误。它在介质中创建一个日志文件, 但没有错误。我的日志文件包含以下内容：

---Downloaded files---
The import files for: demotheme were successfully downloaded!
Initial max execution time = 300
Files info:
Site URL = http://demourl.com/live/demotheme
Data file = /opt/lampp/htdocs/live/demotheme/wp-content/plugins/demo_plugin/inc/importer/demo-files/content.xml
Widget file = /opt/lampp/htdocs/live/demotheme/wp-content/plugins/demo_plugin/inc/importer/demo-files/widgets.wie
Customizer file = not defined!
Redux files:
options -> /opt/lampp/htdocs/live/demotheme/wp-content/plugins/demo_plugin/inc/importer/demo-files/options.json 


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


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New AJAX call!


---Importing widgets---
Primary : 

Search - No Title - Widget already exists
Post List - No Title - Imported
Recent Posts - No Title - Widget already exists
Recent Comments - No Title - Widget already exists
Archives - No Title - Widget already exists
Categories - No Title - Widget already exists
Meta - No Title - Widget already exists

Secondary : 

Tag Cloud - No Title - Imported

Footer 1 : 

Text - About Us - Imported

Footer 2 : 

Navigation Menu - Useful Links - Imported

Footer 3 : 

Custom HTML - Working Hours - Imported

Footer 4 : 

Custom HTML - Newsletter - Imported



---Importing Redux settings---
Redux settings import for: options finished successfully!

以下是我的环境详细信息：

1. 托管服务器php版本：： PHP版本5.5.38
2. WordPress版本：5.2
3. 一键演示导入版本：2.5.1

请说明为什么会出现此问题？

#1

500错误表示PHP语法错误如果使用ubuntu服务器, 请使用此命令检查语法错误。

tail -f /var/log/apache2/error.log