My workaround doesn't seem to be a good idea after all.
After saving the text and reloading the content, an additional "?" (original content was "123") appears.
The error usually occurs only the first time you save.
If I overwrite the content after the 1st save and then save again, the content is fine (except for the extra line breaks)
I have attached my test project, it is the same as for the case TMSFNCWXHTMLMemo - HTML import incorrect
<!DOCTYPE html>
<html>
<head>
<style>
body {
font-family: "Segoe UI";
}
</style>
</head>
<body>
<p><span style="font-size: 14px;">?123</span><br></p>
</body>
</html>