I have a "small" issue when using the (blob)brush or pencil tool in AI, with my wacom. I experience a small jump, where the brush size indicator and the brush tool icon seperate for a distance before the brush size indicator catches up with the icon. I the video below, it is screen recorded as a lag with a sudden jump of both indicator and icon jumping together, but in reality, they seperate as show in the picture.
This only occures in AI and only when using my wacom. I don't have the issue using a mouse, or when using the wacom in photoshop.
I have tried using CPU preview and closing down the info panel as other post suggest, without luck.
My wacom is a cth-470 and the driver is updated to 5.3.5-5 which should be the latest. I don't think it is a hardware issue. However my graphics card is an old NVIDIA GeForce GTX 660 Ti, ten years!
Sorry to hear about this experience. I would request you to share some more info about the exact version of Illustrator and the OS, and since when are you facing this problem?
Also, try removing and re-installing the Wacom drivers and resetting Illustrator's preferences by following the steps shared in this article (https://helpx.adobe.com/illustrator/kb/troubleshoot-preference-issues.html) and sharing your observations. Disclaimer: Please note that resetting preferences will remove all custom settings, and Illustrator will launch with the defaults. You may take a backup of these settings from the location mentioned in the article.