It's probably rather a request for improvement than a bug.

When using items with flexible intervals only (regular interval set to 0) behind proxies then the calculation of delayed items is not correct.
As soon as the time window of the flexible interval ends (5mins/day) the corresponding item gets calculated as delayed.

A quick investigation shows that flexible intervals are not taken into account behind proxies:

1. sed -n '933,934p' src/libs/zbxdbhigh/db.c
   if (0 != proxy_hostid)
   nextcheck = lastclock + effective_delay;

1. grep -A1 "!= \$row['proxy_hostid']" frontends/php/queue.php
   if(0 != $row['proxy_hostid']){
   $res['nextcheck'] = $row['lastclock'] + $res['delay'];
   –
   if(0 != $row['proxy_hostid']){
   $res['nextcheck'] = $row['lastclock'] + $res['delay'];
   –
   if(0 != $row['proxy_hostid']){
   $res['nextcheck'] = $row['lastclock'] + $res['delay'];

I'm sure there was a good reason for this. But is it intended to work this way for above mentioned scenarios?