ClangFormat destroys formatting in the whole file on saving

Sometimes, when the edited .cpp file is saved, ClangFormat removes any indentation from the saved file before it is written to filesystem. I.e. the file is saved with completely destroyed formatting and there is no way to restore it.

I'm attaching a screencast with this issue being reproduced. I'm editing a .cpp file and then press Ctrl+S to save it. Then I press Ctrl+Z to undo the formatting and you see that the restored formatting is marked with red bars on the left, i.e. it is treated as modified content, compared to what is saved in the file. Saving the file again destroys the formatting again.

This doesn''t happen with the builtin code formatter.