The following ad: ads/www/delivery/spcjs.php?id=1 fails to load (after 40s), takes some time but the whole side is depending on all elements to have finished loading before DOM is really presented.
maybe post-load the ad?
solution for everyone atm who doesnt want to wait 40s: go and go become a Patreon! or using ad blocker
still not nice to let the client wait till it times out, because of a small ad frame, instead of showing the page. (Chromium Version 50.0.2661.94 (64-bit) here, idk if firefox or similar do the same, but much likely)
if you by "heavy" mean that you do use adblock, then you are not getting the bug, yes, because said frame will be filtered and your browser does not load it and therefor also won't wait till it times out.