When I click the trace of an error, I'm being let to a "Missing Trace Spans" page, what does that mean?

The "Missing Trace Spans" is caused by Orphan Traces and Broken Subtraces. In the linked docs, we detail the reasons this may be happening, and what you can do about it.

For example, if you have a very low traces sample rate, it most likely means that the spans from this trace were not sampled. This hypothesis is enforced if we take a look at the corresponding error event's JSON. If we go to the "_dsc" section, we see the entry "sampled": false, which means that the spans for this trace were not sampled.

Therefore, you might want to consider raising your traces sample rate.