Steps to reproduce:

Changes in configuration:     None, happening since update to zabbix 6

Reproduce:                        

Navigate to Monitoring-> Latest Data-> Select a host (happens with all hosts and different templates)-> select an item and go to the Graph of that item.
Select this week so far, data is showing as expected. Select Previous week or This week and Zabbix says there is no data to show. A manual selection of time ranges only works when selecting a maximum of 5 days, 4 hours, 26 minuts and 15 seconds... (1 second extra results in no data) 

If I try this with the same item but instead of a graph I want to show the values I get all the values shown as expected. So it seems to be a problem with the graphs.
Problem also exists when going to graphs from Monitoring->Hosts->Graphs

Same happening with previous Month (although it  seems to be that Zabbix limmits the showing of history data to a week since version 6)

I get no errors in the front end of Zabbix, none in the server logging and none in httpd or php logging.

See the screenshots attached for a working/none working situation.