Does anybody have some background on this issue / experienced this ?
You couldn't make up the TAC response I had. Bug currently lists v12.0.0-419 / 12.5.0-066
"After doing a research" (you mean googled cisco bug fix site)
"I found that there are not bugs reported for errors on syslog servers on v12.5.0-059, it means that if you upgrade and everything goes fine we can confirm that the version is good for syslog, if not, you will be the first case and we will need to attach that version on the bug file in order for us to fix it on a later time"
Don't fancy being a guinea pig - where are unit tests in this 'agile' world nowadays.
Thanks Paul