SpongeVanilla downloads page error

There looks to be a problem with accessing older builds of SpongeVanilla using the ‘Next’ button on the Sponge Vanilla Downloads page:

edit: doesn’t seem that my screenshot has worked, so copy-paste of the message instead:

#Error 503 first byte timeout
first byte timeout
###Guru Mediation:
Details: cache-lcy1147-LCY 1477559425 4156151250

Varnish cache server


This is for weeks now, this also happens on the API downlaod page.