print view from fast to not working

[oetiker]

Hi

I have with some user accounts on my single head Zimbra 8.8.10_GA_3041 host problems with the print view (press p) on the email.

emails are like 2 lines of text....

some accounts are showing the view in 1 second other account having 30 seconds and there are accounts they the print view is not working...
after 1 or 2 minutes there is this error message:

HTTP ERROR 504
Problem accessing ZCS upstream server. Reason: Cannot connect to the ZCS upstream server. Connection timeout.
Possible reasons:

upstream server is blocked by a firewall
upstream server is failing to send back the response in time
upstream server is down
Please contact your ZCS administrator to fix the problem.

[DualBoot]

Hello,

maybe the DoSFilter ?
any clues in the log ?

Regards,