packet loss inside VPN tunnel, but not on outside between the two SSG's

I am having an awfull few days, can not get my head around this problem.

I have a VPN tunnel between an SSG140 and a SSG5, the SSG140 is in Belgium, the SSG5 is in Hong Kong.

People in the Hong Kong office are complaining that traffic is not flowing when using the tunnel to Belgium, they have no issues with other traffic like going onto the internet.

I started two MTR's and I see little to no packetloss when pinging the untrust interface in Hong Kong from Belgium.

But I do see 16 % packet loss when trying to ping a printer in the Hong Kong office thru the VPN tunnel.

There are no clear errors in either device log's.

Can anyone point me in the right direction please ?