  [...] We present a singlepulse search method, improving on commonly used
neural network classifiers thanks to the filtering of radio frequency
interference based on its spectral variance and the magnetar's rotation. With
this approach, we were able to lower the signal to noise ratio (S/N) detection
threshold from 8 to 5. This allowed us to find over 115,000 spiky single pulses
- compared to 56,000 from the neutral network approach. Here, we present the
temporal variation of the overall profile and single pulses. Two distinct
phases of different single pulse activity can be identified: phase 1 from
December 2018 to mid-2019, with a few single pulses per hour, and phase 2 from
September 2020 with hundreds of single pulses per hour (with a comparable
average flux density). We find that the single pulse properties and folded
profile in phase 2 exhibit a change around mid-March 2021. Before this date,
the folded profile consists of a single peak and single pulses, with fluences
of up to 1000 Jyms and a single-peaked width distribution at around 10 ms.
After mid-March 2021, the profile consists of a two peaks and the single pulse
population shows a bimodal width distribution with a second peak at 1 ms and
fluences of up to 500 Jyms. We also present asymmetries in the phase-resolved
single pulse width distributions beginning to appear in 2020, where the pulses
arriving earlier in the rotational phase appear wider than those appearing
later. This asymmetry persists despite the temporal evolution of the other
single pulse and emission properties. We argue that a drift in the emission
region in the magnetosphere may explain this observed behaviour. Additionally,
we find that the fluence of the detected single pulses depends on the
rotational phase and the highest fluence is found in the centre of the peaks in
the profile. [...]
