I don't know how callerid works in France, but in N. America the PSTN callerid is transmitted between the 1st and 2nd ring. The RingDelay is needed to give the OBi time to receive the callerid before processing the call. If RingDelay is set too low, the OBi will not see the callerid.
Also, do you have the correct CallerIDDetectMethod for France? I can't help with this.