When using the nuget package of this project, I notice that ResizeObserver relatively imports the js file (e.g. http://localhost:1/my-path_content/OxyPlot.Blazor/OxyPlot.Blazor.js (no slash in between my-path and _content, but this is probably due to our side format).
The cause of the issue is the relative path import here.
As far as I know, most application use the same wwwroot at the root, so using absolute import (/_content/OxyPlot.Blazor/OxyPlot.Blazor.js) facilitates the integration of this awesome library