Test mode "Step" does not advance to the next image group for a multi-page TIFF?

I’m not sure if this is a bug or if I’m just using this wrongly. I have a single multi-page TIFF file (time series) with three channels. It gets correctly loaded, and in meta data I can see it gets correctly detected as 3 channels and 48 time points. I am using grouping by time point.

When I execute “Test Mode” and repeatedly click “Step”, I can see the figure with results for the first time point, but no other time points. Repeatedly clicking “Step” seems not to advance to the other images in the series. Repeatedly clicking “Next Image Set” also seems not to advance to the other images in the series. How to step to the next group in test mode?

When I disable grouping, it works.