Qt Quick Applications display texts abnormally on android OS

We built a video recording app for andriod OS with Qt Quick，using "Text" in qml pages to show texts in the app. There were several qml pages that can switch to each other in the app. When the app started at the first time in andriod OS, the "Text" in main qml page showed texts normally, but when we switched to other qml pages or then back to the app's start qml page, the "Text" in all qml pages displayed text abnormally as showed in attachments.