Committees are bad at being responsible or doing things ; it may be better to designate a person (role), who reports on the results to the SST.
All KPMs and other regression monitoring metrics will be calculated on a regular cadence (daily if possible). They are monitored by the SQuaRE scientist, with status periodically reported to the System Science Team (SST). Any major regressions are be brought to the attention of the SST, along with an initial assessment of the problem. The SST may recommend (to the DM Project Manager) further actions, including performing additional testing, broader root cause analysis, documenting the regression, scheduling the fix as well as assessing the priority of regression fix relative to presently scheduled work.
My only remaining question is whether it should be the SQuaRE scientist above, or the SV Scientist, with these responsibilities. I originally thought the latter (so that the SQuaRE scientist can focus more on the deliverables – JupyterLab, SQuaSH itself, etc.), but whatever would work best between you and Michael Wood-Vasey may be the thing to do.