When filtering alarms in Operator Console Alarm View, if you click "Select All", only 50 alarms are acknowledged, even though more than 50 match the filter.
Release : 20.3
Component : UIM OPERATOR CONSOLE - ALARM VIEWER
This is due to "lazy loading" of alarms, to prevent hundreds or even thousands of alarms from loading at once which would cause performance issues.
To work around this issue, you can scroll down continously, which will load more and more alarms, until the full list is loaded. Then "select all" will select all the alarms.
If there is a horizontal scrollbar present in the view, clicking this will also load 50 more alarms, and you can repeat this until all the alarms are loaded.