EVE Technology Lab

So, I'm trying to create a spreadsheet in google spreadsheets to calculate prices of ships and items, so I can count these up, import them and add a markup. I use eve-central api to pull xml prices, using the 'importxml' function, if I load the spreadsheet they will all pull correctly, however after some time, some of them will will return a '#N/A' result as can be seen here: http://i.imgur.com/DVbMKJF.png , because of this my further calculations won't work. The second problem lies in 'evec_api/marketstat/type/sell/max' for some reason I can only use this one, and not '/evec_api/marketstat/type/sell/min' which won't pull data for some reason. If someone could help me, that'd be appreciated as I have no clue what I'm doing wrong.