We have two fields "Time of first response" and "Time to response" to track our SLA's. We recently migrated an issue to a new request type and changes the status of it.
Unfortunately, this caused the date used for "Time of first response" to update to the current time and means our reporting is way off now.

I believe these are custom fields, as they are both named "customfield_nnnnn" when getting the data from the JIRA API. Also worth noting that the customfield doesn't appear in
https://xxxxxx.atlassian.net/rest/api/2/issue/issuenumber/editmeta
Is there a way I can update this field to the correct value either through the front end or JIRA API?
I've used several different variations of this request body, but I think I'm probably way off:
{
"update":{
"customfield_10131":{
"completedCycles":{
"1":{
"operation":"set",
"stopTime":{
"jira":"2020-03-06T11:59:30.530+1100"
}
}
}
}
}
}
(That might not even be valid JSON, I've been messing about with it so much).
I believe this is the correct path to the data in the JSON output:
['fields']['customfield_10131']['completedCycles'][1]['stopTime']['friendly']
There is an array inside 'completedCycles' with the original version of the data and the new incorrect version. Not sure how relevant that might be.