Thorntons posted mixed trading data for the 15 weeks up to 25 April, as its FMCG business contributed to a sales decline.Giving details in an update on Wednesday, Thorntons said its retail division had positive sales growth over the key Easter and Valentine's Day sales, but lower than usual results over Mothers' Day.Additionally, its FMCG division suffered on account of trading issues in its UK commercial channel which contributed to an overall sales decline of 6.7% to £26.5m. Meanwhile, international sales, accounting for 2% of headline sales, decreased by 15.1%.The Thorntons franchise sales declined by 15.2% but consumer direct sales increased by 10.5%.Thorntons' Chief Executive Jonathan Hart said, "The sales decline in UK Commercial is now solely due to reduced levels of orders from one customer which has continued into the second half of the year."Investment bank Northland Capital Partners believes that while the share price has recovered from its lows in February, issues within FMCG business and given the difficult trading environment within the UK, commercial investors should still be cautious on the stock.