What would you estimate the results of a disruptive effect that occurs while a magus is in the process of casting a spell?
For example, a spell like Curse of the Unruly Tongue (ArM5 p.134) has a clear description that states that spoken spells are at -6 to the spellcasting roll. What if that effect begins while you are already casting? Would you impose a Concentration check? An additional Botch die?
As another example, the description of Spasms of the Uncontrolled Hand (ArM5 p.134) does not specify any clear penalty to spellcasting. What would you impose as consequence if the target was using gestures? Simply a penalty to spellcasting? Something more (Concentration check, additional botch die)?