there are at least three main causes of crashes:
1. possible bugs in the Nokia code: PR1.2 has fixed a few
2. possible bugs in enhanced kernel patches or enabled features
3. undervolting in your configuration

1. can be detected if it crashes with the stock kernel
2. can be detected if it crashes with the default settings
3. is quite likely as every device is different and some devices
might not even tolerate lv. often is crashes only when the DSP is used (video etc.)
as it requires extra power.

If you want to find your individual lowest stable settings have a look at the
kernel-config lock command.

I have to repeat it as many people don't read the wiki:
the lowest frequency is not the idle frequency. IDLE = 0Mhz!