Meaning of phrase and reason for using 'cause' and 'caused'

[Tan Elaine]

Since cutting over to our back-up system mid-day on Tuesday, 13 September, our information technology team focused their efforts on identifying the root cause of the technical problem which caused our banking channels to go down from 9:00 am for more than three hours - services were restored progressively from 12.20 pm and were fully operational by 1.00 pm. Our team was determined to find and fix the problem so as to ensure there would be no repeat channel outage.

1. What is the meaning of 'cutting over' ?

2. Is it correct to use 'root cause' and then 'which caused'?

Thanks.

[Tdol]

1 Changing/switching
2 Yes- it's not particularly elegant, but it's not wrong