Here is what I have for this light curve, calibrated to G-band. It agrees quite well with that presented above, esp the transient brightening around 2459190. (Disregard the outlier around 2459200 due to overexposure.) I don’t have the continuity to confirm the undulations of ~1day mentioned above. But I have seen oscillations with a variety of short periods. I wonder if the data used to create the combined BAA/AAVSO figure is directly available so that I could more closely compare?
I see this has now faded to Vmag ~15 so time for perhaps a last low resolution spectrum. It shows a nebula type spectrum with strong forbidden emission lines, particularly [OIII] and a very weak almost undetectable continuum (The Y scale is relative to the continuum at 5500A and the signal/noise in the continuum is down in single figures). In fact I estimate 78% of the light in the V passband comes from just the [OIII] pair of lines at 4959/5007 A