O3 demo: Why does it keep going down / Error 502?

Our O3 Demo (o3.openmrs.org) keeps going down - by which I mean, you see this page (like right now):

This is embarassing and problematic given that 40% of all OpenMRS.org visitors click on “Demo”.

What is the root problem here? How can we stop this happening?

@dennis @jayasanka @ibacher @dkayiwa @raff

p.s. Test3.openmrs.org is in the same state.

I have just re-built release 3.0.0-alpha.19 in both test3 and o3 and this fixed the 502. But would very much like for this to stop happening.

Thank you @grace for fixing this issue!