Posted: 14/06/2014 at 14:45
I think this could be a pollination problem - I've done a bit of googling which confirms that this can lead to misshapen and mal-formed fruit http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=2739
I hope that's helpful
I would add that my autumn fruiting Polka raspberries crop heavily with no problems - I think this is helped because they flower later in the season so there are more pollinators about. Not much help to you now I know, but I thought I'd just pass it on.