I have to ask the obvious question, @alex:
Since Smart Lighting is just a SmartApp like the ones anyone in the Developer Community can write, why not make it open source? This way the tremendous well of volunteer resources here can contribute to:
(a) Finding the cause of this issue ... it may be particularly easy if the version control (git) change history is also published; and
(b) Helping to avoid the introduction of this type of issue to platform wide release by participating in code reviews and Beta testing for a short period prior to each update.
Certainly some portion of SmartThings's platform and even SmartApp and Device Type Handler code will always be "proprietary". As co-founder of SmartTiles, I know there are good justifications for proprietary code.
I think that the code for Smart Lighting, however, and perhaps even Smart Home Monitor, do not represent "trade secrets" that would undercut SmartThings's commercial success if openly shared.
Regardless, even if the code must be kept closed, option "(b) pre-release in-the-wild beta testing", can still help significantly ... even if only for a day or two for minor updates!