Issue
The SLA notifications are sent out at the same time for 25%,50% and 75% completion.
Release
All releases.
Cause
The most probable root cause for this issue is that the 'Duration type' field on the SLA Definition is empty. It has to be either a 'user-specified duration' or a 'relative duration'.
When the 'Duration type' field is empty, then the SLA doesn't understand whether to consider the 'user-specified' duration or a 'relative duration'. So the duration will be considered as 0 and it triggers 25%,50% and 75% completion notifications all at the same time.
Resolution
Set the 'Duration type' field on the SLA Definition to either a 'user-specified duration' or a 'relative duration'.