Space is added between page numbers when importing from RIS
When importing from RIS format (exported from Reference Manager 11), which contains both starting and ending pages fields, Zotero produces something like "p1 -p2" in the pages field, i.e. it adds unneeded space in between. May be, there is some logic in this behavior, but personally I consider it a bug, since I have to manually correct each entry after importing.
SP - 159
EP - 228
And, if I look at it in hex editor, I get ODODOA at the end of each line. So there are two options: 1) space between "-" and number get parsed, but then the same problem would be visible in other fields, which is not the case 2) the extra carriage return (OD) symbol at the end (I have no idea, why Reference Manager uses such redundancy in end of line) is converted to space. The latter seems more probable and I think it is not good behavior for Zotero to convert not-printable characters to space.