(Not sure if this is related to Bug #14907) In the view of a record in OPAC, there is a link "Browse Shelf" next to the call number in the item information. The surrounding records displayed are sorted by their call number but not correctly, e.g. 2 comes after 19, and 16 after 159, whereas it should sort numerically like this: 2 - 19 and 16 - 159.
Just to check: does the sorting work ok for you in other places? For example the inventory list? You could also try a report like this: select cn_source, cn_sort, itemcallnumber from items order by cn_sort This should reflect how Koha thinks the callnumbers should be sorted.
With the SQL query, I get results sorted in the same (numerically incorrect) way as described.
I don't believe it's a bug then, it's a configuration issue. Koha will generate a sorting form of your callnumber (itemcallnumber) from the classification source (cn_source). It's saved to cn_sort and used in a lot of places for sorting callnumbers. If you check the manual for classification sources, you'll find information there about the 3 algorithms Koha has to do that (DDC, LOC and generic). Sadly no RVK and similar yet (I'd be happy to see that added :) )