Um, Steve, something is wrong in your analysis: base-files is fully configured before bash is unpacked, and when _unpacking_ bash it tries to process the trigger (i mean, there's no "Setting up bash" in front of it; but maybe dpkg processes triggers before printing that).
The odd thing here is that apt should be calling dpkg with --no-triggers, unless we're doing TriggersPending, ConfigurePending, or the last step in the run - and that's not happening AFAICT.
@Kees long stretch, but maybe you have a dpkg.log from that?
Um, Steve, something is wrong in your analysis: base-files is fully configured before bash is unpacked, and when _unpacking_ bash it tries to process the trigger (i mean, there's no "Setting up bash" in front of it; but maybe dpkg processes triggers before printing that).
The odd thing here is that apt should be calling dpkg with --no-triggers, unless we're doing TriggersPending, ConfigurePending, or the last step in the run - and that's not happening AFAICT.
@Kees long stretch, but maybe you have a dpkg.log from that?