I have an IDM 3.5.1 idvault connected to an AD system.

The idvault is authoritative and if changes are made in AD the filter
resets attributes back to the Edir values. This worked fine until I
made a change to the format of 'initials' .

The output transformation rule uses normalize-space to tidy up the
initials then reduces them to 6 character to match AD.

The problem then occurs when changes are made to the initials in eDir
and they are written to AD in the different format - AD then tries to
write the new initials back to eDir, which then get reset by the
filter to the eDir value which then get writen to AD in the new format
ad infinitum.

I'm sure this is potentially a common problem and I've made a
fundamental mistake - what can I do to fix this?

I've changed the publisher filer for 'initials' to ignore for now.

Trace available if required, but it looks like a simple 'n00b' error