egaona wrote:

I've noticed that there are some task or defect work items showing up
in more than one build. Other work items, just show up on 1 build.
So I'm trying to understand the logic how some work items are showing
up in multiple builds, while others on just one. Is this because
the Found In field is not set or something else?

Builds can be configured to accept changes into a repository workspace
before starting the build. For every change set that is accepted into
the workspace when a build is started, an "Included in build" link is
added to every work item associated with that change set.

So if a work item has just one "Included in build" link, then change
sets associated with that work item were accepted into the build
workspace in only build.

If a work item has multiple "Included in build" links, then change sets
associated with that work item were accepted into the build workspace in
multiple builds. This can happen if the work item has multiple change
sets that were delivered to the stream at different times, or if a
change set was delivered to multiple streams, or if there are multiple
builds that are building from the same stream.