Using sed or awk to remove near-duplicates

I currently use the following to get as close as I can do to a file

cut -d ' ' -f 3- /var/log/issues.log | sed -E 's/[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}//g' | sort -u 

So far it gets rid of the timestamp at the start of each line and removes the IP address.

However I'm still left with dozens of line of the format(s)

Failed login from for A Failed login from for B Failed login from for C Failed login from for D Failed login from for E Invalid heartbeat 'A' from Invalid heartbeat 'B' from Invalid heartbeat 'C' from Invalid heartbeat 'D' from Invalid heartbeat 'E' from 

How would I further amend my command to take these "near" duplicates away leaving only. A, B, C, D and E could be any string.

Failed login from for Invalid heartbeat from 

Thanks

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