I assume you're using Title Designer and have chosen a Hebrew font from the Font/Paragraph section, and then when you try to add a Scale keyframe (either from the Object Settings section or on the TD timeline at the bottom) the text disappears. Is that correct?

I just did some testing with the Segoe UI font using Hebrew characters from the built-in Windows Character Map app and I see the same problem as soon as I place a Scale keyframe. Additional keyframes don't bring the text back and it remains missing until all Scale keyframes are removed.

Interestingly, Cyrillic and Armenian characters are located just before the Hebrew ones and they work fine. So do the Hebrew accent characters, but as soon as Hebrew letters are used the problem shows up. Same with the Arabic characters that follow the Hebrew alphabet, but the Scale keyframes work normally again once you start the Latin characters immediately following the Arabic ones.

I think you should contact Cyberlink tech support to report the issue. This isn't the first time PD has had problems with non-latin characters, as can be seen in this post.