Thanks for the case @Yousef Darrat.

There is a clear intermittent non-tracking of P waves, with no ventricular spikes fired, hence pauses that are likely causing his dizziness.

"Ventricular non-capture" is incorrect since there is no visible ventricular spikes fired with no QRS following them. "RV under-sensing" will cause the opposite (i.e., inappropriate ventricular spikes fired), which we don't see here.

"RV oversensing", which is in general very rare, may explain the absence of ventricular spikes, however, this is unlikely, unless it is very random and intermittent. Also, this has to be proven using EGM for PM to that will explain the mechanism of oversenting. Moreover, the absence of ventricular firing here is appears to be somewhat systematic with only certain P wave not followed by ventricular tracking, which will make it more suspicious for a functional behavior of the device, leading to ignoring some of the "P" waves (overlooked).

Although his sinus rate is at or slightly above 100 bpm, will vote for "upper rate behavior", although that is usually seen at very high-tracking rates close to the 130 bpm by default in most devices. I suspect that it is likely induced by the programming change made by his cardiologist, especially if that involves factors affecting total atrial refractory period (TARP, i.e., PVARP and AVI).