Thanks for all your troubleshooting on this guys - I’ve referred back to this thread on a few occasions now as I’ve had the erroring Dashboard problem and the non-functional Package Manager problem on several occasion after upgrades to MODX 3.x.
The Updates dashboard widget definitely seems to cause problems on some sites but not others. Removing it from the Dashboard seems to fix it.
In my latest site with the Package Manager problem, deleting the extra, findParent from the modx_transport_packages table fixed the problem. It’s a very old extra [from a very old site!] so perhaps not surprising that it was the culprit - but it does just seem that some extras mess up the 3.x Package Manager.
Thanks again 