Ellis repeatedly refers to Jonathon Richardson (brother of Benjamin and W.H.) as Johnathon.
Until page 335 where he refers to him as both Johnathon and Jonathon.
One reason could be because in 'Richardson Papers no 41 Bankruptcy notices' (see pp 348 note 82), Jonathon seems to have been mentioned as Johnathon - (see p329) where Ellis quotes
'B. Richardson on 5 May, 1848 mortgaged all his interest in the glass trade to W.H. and J. Richardson as security of liabilities incurred by them in their bills without their knowledge and consent as alleged by Mr Johnathon Richardson'.
There is also a note on pp 347 Note 60. 'Johnathon Richardson, son of Joseph Richardson and his wife Martha, nee Haden, bap. 24th Aug 1806 Kingswinford.' where it refers to him as Johnathon not Jonathon - this might be the primary error?
I've no idea why Ellis then switches to Jonathon.
There is also another misconception in the sentence where he makes that switch -
'Benjamin was sixty-one and Jonathon(sic) fifty-nine years old.' (pp335)
where from the information Anne has given, Jonathon had already died by the time Benjamin was sixty-one.
I suspect that because a death was not established for Jonathon (brother of William H and Benjamin i.e. 'our' Jonathon) assumptions were made that he was still alive.