Bret Devereaux

...a large, interest-free, 3-year loan to bankers when loans at the time were rarely extended for more than a few months. This was unprecedented, and was unlikely to be a response to a minor matter.

It was not unprecedented. Tiberius' two immediate predecessors, Julius Caesar and Octavian had made similarly sized donations to either the people of Rome, the public treasury, or both.

Octavian (Augustus) is at pains to point out that he made similarly massive donations to the public (RG 15) and that he bailed out the public treasury no less than four times, at a number significantly greater than what Tiberius spent (RG 17)

I suppose at some point it depends here on what we understand as a major crisis - evidently significant enough to drag in the emperor...but mostly because its consequences were confined to the landholding elite that dominated Roman politics.

I think the relative weight the sources give to it compared to the Sejanus affair - which occurs immediately prior in Tacitus and Dio (and chronologically) is illustrative. It is essentially a footnote in the back few years of Tiberius' reign.

I should note that, looking at his article, Bartlett's claim of evidence of 'significant capital outflows' (he more accurately notes it as a shortage of money in circulation, which is, I'd argue, more accurate) is balanced on T. Frank, "The Financial Crisis of 33A.D." (1935)

Given that the study of the Roman economy has turned on its head twice since 1935, I'd myself have been pretty cautious citing Frank on such a point. I too have piled through his An Economic Survey of Ancient Rome (1933/1940)...

...but our sense of money flows and the money supply in Rome has changed a LOT since then. Thanks to a mix of coin die studies and Greenland ice cores, we know that, at least empire-wide, the money supply was expanding in this period.