I'll preface this with a note that I've only ever worked on my own pens so am not a nib meister. I have had a large number of pens though, a good number of which didn't write well. It's useful to know what paper and ink that is though.
I've never seen a stub with good alignment that was quite that bad but I have had two distinct problems on stubs in the recent past; one factory and the other 'meistered'
You mention there is only marginal baby's bottom, check that each tipping surface is either absolutely parallel or such that centre, tine gap is the first part to touch the paper though: I had a stub that wrote a bit like yours that didn't show baby b at the gap in the tipping but the outside edges rode on the paper before the tine gap area did, result was the same. I managed to straighten out the tipping surfaces and it came good - I went very slowly so it took a while.
The other case I had was simple overpolishing, whether this was made worse with baby b or not, it wrote okay on more absorbent paper, the polishing was so high on the large tipping area though that the ink just wouldn't flow in that contact surface when writing. I got more partial lines than you show above, with less of the stop-start flow your pen exhibits but still, it was improved hugely with a very light swipe or two across 6000 grit mesh, gave the ink some texture on the nib to break the surface tension - that's my theory. (it helped that I dislike glassy smooth nibs anyway)