Trackpad sluggish when charging or not touching unibody (weird)

MacBook Pro 13" 2017

If I'm not charging, it's flawless, however when I have the (Apple original) charger plugged in (usbc TB3 directly into usbc port)... And use one finger on the trackpad the cursor is sticky, glitchy, not fluid like it should be, but the weirdest thing is when my hand has even slight contact with the unibody area around the trackpad (such as the ridge to lift the laptop open) (or the palm rest to the side of the trackpad)... It works as normal.

As far as I'm aware this just started suddenly, however it may be that I've only just noticed it as I don't usually use the laptop whilst it's charging, and the few times where I do - I have probably always made contact with the unibody...

im actually restoring to factory settings as we speak, however the issue is persisting on the install MacOS menu so I doubt this is going to fix it

Any ideas?