Experiencing a problem with MPLS (printing)

We are currently implementing a VPN (MPLS) solution for a client and experiencing problems. On the sites that have been cut-over to MPLS, those branches are experiencing major printing problems. Packets of data are being loss (small amounts eg, +- 10 in a 1000) and stalling printers. The company uses an online system, Kerridge, and with the printers stalling, the customer cannot trade.
Bandwidth usage on the lines is only +- 30%.
Any suggestions, advice on things to check or comments please? Much appreciated.