Resolved Articles Addon thumbnail size fixed at 200x200

I hope you can help but I'm trying to use the articles addon inside PageBuilder but my thumnails are fixed at 200x200 pixels which is too small (see image attached).
I've tried changing the thumbnail size in my template settings to 600x300 and I've cleared my cache but it hasn't changed.

Where can I find that intrinsic 200x200 setting? Presumably I can override it somewhere within Page Builder?

Thanks,
Mike