[safari] changing format doesn't work in some cases

[haven2world]

Describe the bug
when I input "abcdefghe" in the demo, I can change the format on "abc" successfully, but then I cannot change the format of "def" for some reasons

To Reproduce
Steps to reproduce the behavior:

1. Go to roosterjs demo in safari
2. Input "abcdefghe"
3. Select "abc"
4. Change its font size to 8 (working)
5. select "def"
6. Change its font size to 72 (not working)

Expected behavior
"def"'s font size should be changed to 72

Screenshots

Screen.Recording.2025-12-23.at.14.32.47.mov

Device Information

• OS: Mac OS
• Browser safari