Two bands, not one
Every film, seal, sugar, metallic and moisture barrier grade we supply runs the film coating band. Aqueous sits at 35 to 40 degrees at the tablet bed against a 75 to 80 degree inlet, non-aqueous at 30 to 35 against 60 to 65. Every enteric grade runs a third, cooler band entirely, 30 to 32 at the bed against a 45 to 50 inlet. That gap is the largest single difference between the two ranges.
What the temperature is doing
An immediate release film only has to form, adhere and look right. An enteric film has to form and then stay impermeable to acid. Those are different requirements of the same dried layer. Polymer applied to a bed that is too warm softens as it lands and coalesces unevenly, and a film that has coalesced unevenly has weak points. They are invisible on a finished tablet and decisive in an acid stage.
Why the inlet drops too
The inlet is what heats the bed, so holding a cool bed means a cool inlet. The consequence is that drying capacity falls, which is why an enteric stage takes longer than a film coating stage of the same build-up. Pushing the spray rate to recover the time puts water or solvent into a bed that cannot clear it, and that produces picking rather than a faster batch.
Where this shows up
The failure mode is a batch that passes visual inspection and fails the acid stage. Before looking at the film, check what the bed actually ran at rather than what the recipe says, because inlet temperature and bed temperature diverge as the charge changes.