Unfortunatley we need to develop an Import plug-in helper with dev mode OFF, for - according to Brad at P&T:
devMode uses a lot more memory on a given PHP request and importing probably already requires significant memory, so my guess is that you're running into your php.ini file's memory_limit or max_execution_time limits or something similar.
The Import plug-in is definitely a resource pig. We can't get it to work at all in dev mode. But we need to develop a plug-in using its hooks to help with things it can't handle in our situation (tables, dates, switches) so we're in a tough spot.
According to this article:
If you want a log item to appear regardless of whether devMode is enabled, you can pass true as the third argument to the log() method.
SproutActivePlugin::log('Log this with or without devMode enabled.', LogLevel::Info, true);
Is this accurate?
We've tried it. Doesn't seem to work as advertised. Nothing in the logs unless dev mode is turned on. And when it's turned on the Import plug-in hangs up. We're in a tough spot.
What else should we be looking for? What else can we try?
Craft CMS 2.6.2930 / Import 0.8.28 / PHP 5.6.10
EDIT:
We have increased memory_limit 10 fold (1280M)
We have increased max_execution_time 100 fold (30000)
We have increased max_input_time 100 fold (60000)