I've seen many houses with spray foam and insulation Batts in the joists between the ceiling and attic floor.
What types of issues would there be?
It's not a death sentence by any means - there are many mitigating factors that could make it 'safe' to leave insulation on the attic floor. But generally speaking the recommendation of the experts is to remove it. This article has a nice summary:
https://www.greenbuildingadvisor.com/article/three-reasons-to-remove-attic-floor-insulation-in-a-sealed-atticThe basic issue is that if the attic floor is not really well air sealed (which realistically is often the case), there is air being exchanged between the living space and the attic. That makes the air in the attic more humid than outdoor air, and since when you do spray foam you generally close up any attic venting, there's no way for that humidity to escape outside anymore. Leaving the insulation on the floor means that the temp in the attic in the winter will be significantly colder than in the living space, potentially allowing the spray foam itself to become a condensing surface, which brings moisture problems into the attic.
Most of this is based on the work of the 'godfather' of modern building science Joe Lstiburek - here's his article on this topic of conditioned attics:
https://www.buildingscience.com/documents/insights/bsi-077-cool-hand-luke-meets-atticsBottom line, I would think any type of insulation on the attic floor has this issue, unless it was also an air/vapor barrier (like cc spray foam) - though obviously there's no reason one would have that on the floor and the roof deck.
I've also seen spray foam done and the gable vents were left opened. Was this possibly done to allow for some sort of airflow in the attic?
This on the other hand does sound like a death sentence (though of course I'll caveat that I'm not anything close to an expert on this subject). You fix the moisture issue, because it can escape to the outside, but you're killing the effectiveness of the insulation. When the insulation is on the floor of the attic, it's okay to have a vented (ie unconditioned) attic space because the insulation still separates between the living space and the unimpeded airflow from the outside. But once you move to spray foam, where the insulation is on the underside of the roof, keeping the attic freely vented to the outside just introduces outside air inside the insulated space.