I've been using QuantConnect for about 4 years now and something I've seen over the years that still hasn't been addressed is backend changes being made without any community announcements.  For example, I'll run a backtest and be please with results and then start doing sensitivity analysis on some of the constraints to make sure its a robust signal and then out of nowhere my backtest results will be wildly different.  This tends to happen during data maintenance or something in the backend and the initial results come back after a few hours or so.

This is happening to me as I write this actually.  The thing is, I never really know if the data change is permanent or caused by some other backend process.  So I sit here and I'm afraid to really build anything because I don't know which results to trust.  

It would be really convenient if there was a section on these forums for QuantConnect to release “maintenance times” or “summary of recent changes” or what have you so that the community can get a sense as to what is changing, if anything, at a given point in time.