Failure Of Contactors In 110kw Star Delta Starters

I have an issue with 110kW Star Delta Starters...the application is RAW SEWAGE WATER PUMPS installed in a Sewage Treatment Plant.

Motor Details are as follows:
Rating : 110kW
Voltage : 380 - 480V
3 Phase
Ampere : 205 - 190A
Frequency : 50Hz
RPM : 1476



We have used the following components in the Star-Delta Starter:
Main Circuit Breaker : 250A Frame / 220A rated Motor Protection MCCB
Main and Delta Contactors : 225A
Star Contactor : 150A
Over load relay range : 132A....to....220A
Static Capacitor rating : 32.5 kVAR
Contactor for Capacitor : 95A
Timer used is a normal ON-DELAY timer (not a Star-Delta timer)

The problems we face are:
1. At the time of Starting, there was a spark in the MCCB, the Star and Delta Contactors got welded and the over-load relay got damaged.
2. We have another complaint that there is only one healthy output in the 3-Pole MCCB.
3. In the same MCC, we also have lower rated Star-Delta starters...we have received complaints of the Contactors getting burnt during initial start-up.

Could you please advise the possible causes of these faults and what remedial action I can take. I am attaching the Power and Control wiring diagram of this Star-Delta Starter.Could it be due to use of a normal On-delay timer instead of a Star-Delta timer?

Is there anything to do with the connection of the Static capacitor...As per the wiring diagram the Capacitors are switched on even in Star mode...is this correct...or should we bring the Capacitors on line after switching to Delta mode.

Is the Wiring diagram correct? location of the overload relay,..etc.

Thanks a lot for your advise.