Since some time and for multiple installed Zabbix Server versions we got a strange display error with some items. We're unsure what the issue is because it only affects some items, even when they're autodiscovered templates assigned to one host. Multiple hosts are affected with some randomly items at each one. Some of them are affected, some are not. All items and triggers are working fine, it is just a frontend display issue.

Some items got a red warning hintbox with only a apostrophe inside and nothing more:

'

This looks like only a small display issue, but it's confusing because there seems to be a lot of non working items which are working fine actually.
 
We can easily modify Zabbix files and debug this issue, but we need some assistance to find the right spots.