Please refer to the solution at the end.
You asked what accessibility tool, Bernardo, I too am having the same parent / child role issue, using AXE accessibility tool and although the issue does not appear with me on WAVE, our company policy requires all Outsystems software pass accessibility checks on each of these 2 accessibility tools.


Widget Tree for accordion:
The accordion consists of a tablist of accordion items, each containing address data only, ie no input fields.

AXE advises the following url for the solution, but not sure of solution to this would be in Outsystems: https://dequeuniversity.com/rules/axe/4.3/aria-required-parent?application=AxeChrome
F
As you can see below, the accordion item, has already been assigned (role="tab"), but the list had not been assigned (role="tablist").
This is how I assigned the role of tablist to the list:

By this action, of assigning the list the role of tablist, the critical issue was resolved.
Kind regards
Fearghal