An ETF price might be slightly different than its underlying assets' one because the latter trades in the primary market and the former in the secondary one (font: ETFs bubble see minute 5:30).
Taking this into account, in an hypothetical ETFs / index funds collapse, can it happen that this difference goes off to very high levels?
If so, is technically possible that, after a crash, the ETF's underlying assets' come back to 'normal' values while the ETF itself is stuck at a very low price?