Hi and welcome to the forum!
This error is likely due to very small weights on one of the connections in your model, as it can be difficult to handle these correctly with 8-bit quantization required by Loihi. Extremely large weights can also cause the issue, but this is less common. In terms of debugging, one option is to run your script with ipython --pdb so that you can step into the debugger and print information about the compartment that’s causing the problem. If you give all of the ensembles in your model unique labels, you should then be able to see which ensemble is at the root of the problem, since its label will be passed on to the compartment shown in your stack trace here.
A member of the Nengo Loihi development team, @Eric, has recently created a PR to add objects to all build errors, which will hopefully make it much easier to track down which objects in your model are causing problems. The relevant branch to check out is here: https://github.com/nengo/nengo-loihi/pull/289.
In terms of more general tips, tricks, and pitfalls to avoid when using the nengo-loihi backend, we’ve compiled a list of things here: https://www.nengo.ai/nengo-loihi/tips.html.
We’re always looking to add to this, so I’ll check with the team about providing some more context for users around the role of discretization on Loihi.
Let us know if there’s more information that would be helpful, or you have any followup questions.