Steps to reproduce:

1. Create new webhook
2. Add script "return '{"tags":{"a":1}}';" and select "Process tags"
3. Add macro {EVENT.TAGS} for message type "Problem recovery" in message template
4. Edit user and add two media with this webhhok
5. Make trigger in problem state
6. Make trigger in resolved state
7. Check Reports -> Action log

Result:
two identical tags "a:1, a:1"