Just like subject says: no actions are taken on problem if it gets resolved while escalation is in progress.

Consider the following scenario:
1. There are two trapper items (itemA and itemB) on a host
2. Both items have triggers (triggerA and triggerB) with expression {host:itemA.last()}<>0 and {host:itemB.last()}<>0
3. Both triggers have actions (with multiple operations) attached to them
4. First trigger (triggerA) goes into problem state and escalation process starts (action operations are executed)
5. While escalation is in progress (it may take some time as there are multiple commands) second trigger (triggerB) goes into problem state
6. While escalation is still in progress second trigger (triggerB) goes into normal state (problem on triggerB gets resolved)

No action operations assigned to triggerB will be executed:

Highlighted problem (09:48:40) has no actions executed as it changed it state while triggerA problem actions were executed. Last problem (09:52:35) shows that actions are executed without any problems if escalation is not in progress.