To reproduce:

• 2 hostgroups - test read/write and test read-only group.
• usergroup test group with read/write permissions to test read/write group and with read-only rights to test read-only group
• user some Admin with Zabbix Admin assigned to test group .
• test host 2 is assigned to both groups see screenshot
• login with Some Admin user
• go Configuration -> Host page click on the host name of the test host 2
• change something in profile, click save - you have an error see screenshot

also if you search host by searching field then in results click on the hostname link for viewing profile, you have the error again. (on screenshot also added hostgroup zabbix server fro read-only)