can the location sharing ever be wrong? multiple days?

Location Sharing can only ever be as accurate as your device is capable of reporting, to Apple’s servers, its current location.

If you have a WiFi Only model of iPad, then your iPad lacks GPS capabilities necessary to accurately determine its location - instead estimating its location from database lookup of surveyed neighbouring WiFi networks and location of the “public” internet address through which your iPad connects to the outside world. This method of location derivation can be quite accurate in urban and densely populated areas, but becomes increasingly unreliable in remote or rural areas. If using a VPN or satellite internet connection, the reported location can be wildly inaccurate.

A WIFi+Cellular model of iPad does have GPS positioning capabilities - and providing that the iPad receives sufficient GPS satellite signals, with good relative geometry, should be able to accurately determine its location. If indoors, satellite reception may be severely impaired - causing the iPad to fall-back to estimating its location as described above.

So, in summary, it is technically possible for the reported “shared” location to be inaccurate.