It seems that when setting up dynamic graphs on screens which have an axis set to a value of an item, it does not change when selecting another host.

Example:
zabbix_get -s redmine01 -k vm.memory.size[total]
527548416
zabbix_get -s sauron -k vm.memory.size[total]
2125926400

See how the sauron.png shows a correct graph, but when selecting host redmine01 the graph on redmine01.png does not display the right Y axis maximum value.
However, the graph in redmine01-graph.png is correct.