Below are listed those faults for which 2 or more hours were lost.
When doing large offsets with the telescope at high declination the guide star was lost in each case. This required the need of an very time consuming offset scheme which is included in the total down time reported. In the end it was found that there was an error in the software that calculate the telescope offsets which caused significant errors at high declination.
In the middle of the night the communication was lost with the instrument. At first, resetting the communication (multiplexer) unit solved the problem before it failed completely. The problem turned-out to be with the power supply of the multiplexer which was replaced. We have a spare, but in the future this will also not be a problem as all the communication will go via Ethernet and we will no longer use a multiplexer.