Oof, that sounds nasty. Did it turn out to be a standard-ish formatting with a separator where you break the line after x number of separators? I really dislike having to parse a log like that before just being able to read the log
Fortunately I didn't have to edit the log in-place as we were ingesting it into Splunk, so I just wrote some parsing configuration and Splunk was able to munch on it without issue.