Blocked steering at the Fiat Croma 194 (2.2)

Hello together, read here in the Motor Talk several articles about problems with the power steering. My Croma year 2006 is since last Tuesday after twice blocked steering in the workshop and all are with their Latin at the end. Thanks to guardian angels I had no oncoming traffic when turning at a crossing, because the steering blocked and I came to a stop in the turn-off track of the opposite traffic. After this full braking the steering functioned again as if nothing happened. 5 Minutes later, when turning at another intersection, the steering again blocked. From there, the ADAC went into the workshop in the piggyback pack. When the engine was started to load, why was always displayed in the display “Inertial switch”, which had actually triggered even though there was no external reason for this. After that, the engine could be started and the steering worked again. The workshop could not detect any errors in the steering when reading the fault memory. Only the hydraulic oil level in the balancing tank of the power steering system was slightly below minimum (200ml filled up), where the missing oil has migrated is unclear, because no leaks could be detected, even the cuffs were dry. Fiat TESEO has proposed to the workshop to replace the steering wheel lock and the ignition lock, since a message was filed in the fault memory which read “sporadic ignition lock / steering wheel lock not recognized”. is informed about this incident in writing and by telephone, has not yet contacted the workshop or with me, even after repeated phone calls. Does one of you have an idea where the problem for blocking the steering is to be looked for? The workshop has now carried out several test drives with the vehicle, but can not detect any steering problems. Otherwise the vehicle is in a very well maintained condition, my confidence in the croma is several wheel bolt fractures (during the ride 4 of 5 bolts broken off at the rear right and 6 months later 3 of the newly used bolts broken) and a failure of the ignition coil unit during a ride on the highway with consequential damage catalyst dropped to NULL. The wheel bolt fractures were dismissed by the customer service, since there was no guarantee anymore and there was no damage to property or persons. Would I be pleased for relevant information.