Settlement Cell Data jumping
If it is definitely not feasible data and you can confirm that no such movement has occurred, these could be the reasons:
1) There is air within the tube to the settlement cell. This air pocket caused a the actual column of water to not be transferred into the sensors diaphragm. When you topped up the datum pot the additional pressure of water moved the air pocket which caused the true pressure to suddenly be presented. Can you confirm you are 100% confident that all the sensors have been de-aired correctly?
2) When performing the service you noticed a valve was not open and you corrected this but did not realise that this would effect the readings
3) An air pocket of 40cm was present within the system and the topping up or opening of valves released this air pocket and this in turn increased the readings