the slightest hiccup like Iran being able to sell its oil
??? Iran can sell it's oil. What are you talking about?
Have you paid any attention to the news ?
Iran has high cost oil with breakeven prices above that of many fracking fields.
Iran has few allies or friends because it is a pain in the butt.
It has years of deferred oil field maintenance with accumulated costs that may be in whole number multiples of its GDP and no one wants to invest or work there.
It has lost market share and given its baggage not many countries want the contacts needed for Iran to sell oil to them. India and N.Korea being the big exceptions.
A large fraction of its production is dedicated to its expeditionary forces in Iraq and Yemen.
The GCC is producing all out to ensure that Iran is not competitive in the world market. Despite aid from,Iraq and Syria as co-belligerants in the Shia-Sunni dispute that aid is limited by self interest.
So, no it is a huge question as to whether Iran can as part of reality sell significantly more oil than it did under sanctions?