Hmm… this might describe the jumps, though it is wierd that where we observerd this was ~10 hour after in Experiment 1, but not in Experiment 2 that has been running for 800 hours (experiments were run on separate clusters). Interestingly thoug, after we replaced vials on the 800 hour experiment, the jump occured couple hours in to the experiment - This was not a jump caused by vial change, because the intial readings were fine. The jump happened when long later when we were not there.
Yes, this was the first thing I checked but there was no big jump registered at the moment of these events.
I would also said “other jobs” as potential cause, and yes, in certain cases I observed that there was a yellow warning for RPM=0 and slight increase in temperature (likely due to RPM=0) close to the events. Though, this combination has not been consistent in all the cases.
They are located away from the window and shielded at the corner, so ambient light should not be problem.
I will analyze the IR intensity with plots as you provided in the post: OD value changes after removing and returning vial for photos to see if I am missing some details.