I would recommend reading up on the following KB article: Troubleshoot
spikes and drops in data Your predicament is one that makes data
research kind of fun, since you'll be diving into your data to determine
what the comon ground was. Segmentation will definitely be your best
friend, so be sure to use it liberally t try and identify any common
threads. You can also use workspace's anomaly detection, which might be
able to point you in the right direction of what the root cause was.Good
luck!