While already the proposal default setting for both SPB and MID since its introduction, proposals turn up in the wild without this setting and thus defaulting to -1. This may be due to manual misconfiguration or existing older proposal configurations. For very large runs, this continues to be highly unstable.
Given it's universally applied anyway, it feels safer to enforce this already on the notebook-level to catch such situations. This should be deployed immediately as 3.7.3
Last few months of operation.