I'm getting errors such as "object does not exist" and "not responding" intermittantly on tests that used to run fine.
Many of these are made to work again by overriding the default "auto-wait timeout" of 100ms to 1500ms for the particular action that is failing. I didn't bother trying to see how long is really required. I see no harm in a higher-than-required value since it continues as soon as it can.
If the Auto-wait Timeout field is not shown in the KeywordTest editor, right-click just about anywhere in the test and select "Field Chooser".