Cadence is dropping intermittently during rides to ~40 RPM? Noticed over the last few weeks - recovers but cadence will be relatively static during time that drops are observed. Any similar symptoms been observed?
I think that the Core uses a calculation based on changes in power at different points of the pedal stroke to determine the cadence (i.e. there is no actual cadence sensor). So, it’s possible that at those points where the cadence shows to drop that you just happen to be pedaling with a very smooth power level through the entire pedal stroke, thus ‘confusing’ the algorithm.
It could be dropouts, too, of course, but we can’t see if your power is going the same thing in the screenshots you posted.