There was a report on #dm-square yesterday of blueocean show no test results when there was a failure and all tests were visible in the classic UI. This was fixed by upgrading from BO 1.5.0-beta-2 to 1.5.0, which was planned to resolve the issue with links to triggered builds being broken. This resolved the problem with the reported build:

https://ci.lsst.codes/blue/organizations/jenkins/stack-os-matrix/detail/stack-os-matrix/27893/pipeline/46/

but it appears to have introduced a bug that results no test results are showing under BO when following a link from the classic UI test result view -> BO.