I'm using ProtocolSupport, and in old version holograms could disappear and bug sometimes:
https://i.imgur.com/1HcydOz.png
https://i.imgur.com/24GwuPk.png

Also updates through API is too buggy, hologram jumps, and could cut some lines in old versions.

One more question: could you explain to me, please, how to update holograms (for example timer) smoothly without flicker, using API?

If you want smooth updates you should try updating lines, instead of clearing all of them and adding new ones. That's just what I assume, you should post your code.

I can't fix the problems with ProtocolSupport, you should ask the developer of that plugin.