I see the same issue. I set my meter to log 2 AA batteries, 1s intervals. Very stable 3.812V except spikes at -3.4V. Always same negative spike, but not at repetitive intervals. Timestamps look ok. I think this was an issue several builds ago, but had been fixed. Filtering these spikes out could work for some situations, but if you are looking for some anomaly in the device being testing you may not be certain if it is the meter or the device being measured. Hope this is an easy one to fix.
– — – Duane