I’ve seen other reports of headers disappearing.
It also happens when data is pasted from Excel.
LW Version: 24.2.5.2 (X86_64) / LibreOffice Community
Build ID: bffef4ea93e59bebbeaf7f431bb02b1a39ee8a59
CPU threads: 12; OS: Windows 10.0 Build 19045; UI render: Skia/Raster; VCL: win
Locale: en-AU (en_AU); UI: en-US