To fix the bug described in my previous message, David Bluecame recommended to try setting [font=courier new]adv_auto_min_raydist_enabled[/font] or [font=courier new]adv_auto_shadow_bias_enabled[/font] parameters to true and play with the values of [font=courier new]adv_min_raydist_value[/font] and [font=courier new]adv_shadow_bias_value[/font].
Changing [font=courier new]adv_min_raydist_value[/font] didn't have some effect but [font=courier new]adv_shadow_bias_value[/font] did, the reason why I published the version 1.4.3 (there was only little feedback about it and I'm not sure it's the perfect solution).
Try to set [font=courier new]adv_shadow_bias_value[/font] with a float or double value, not a boolean value. The fastest way to try some YafaRay parameters and get their type is to look at a XML YafaRay example like this one: [font=courier new]bval[/font] is for boolean values, [font=courier new]fval[/font] for float or double values, [font=courier new]ival[/font] for integer values, [font=courier new]sval[/font] for strings.