I can audit the container for duplicates, but I need its contents first. I also cannot publish anything: publishing needs your explicit approval of a named version, and you do it yourself.
What I need (required): 1. The tag list. For each tag: name, type, key ID (for example the G- measurement ID) or event name, firing triggers, blocking triggers, and whether it is paused. I look for two tags sending the same ID and event on overlapping triggers, so IDs and triggers are essential. 2. The trigger list. Name, type and conditions for each trigger. 3. User defined variables. Name, type and what each one reads.
You said you cannot export the container. Tag Manager's help page gives the export steps (Admin, then Export Container in the Container section, then Download) at https://support.google.com/tagmanager/answer/6106997. If that option is not there for you, pasted lists work just as well, in pieces if needed for about 60 tags.
Optional, with the defaults I will use: - Version info: the live version number, and whether the workspace has unpublished changes. Default: not checked, and labeled that way. - Data layer events: the event names the site pushes. Default: custom event triggers are not checked against the site, and I will say so. - Which GA4 numbers look doubled (page views, purchases, all events) and since when. That tells me where to look first. - Which tags the old agency made, if you know. Default: tags are not grouped by who made them.
When I have the lists, I will return inventory counts, duplicates, broken, unused and paused items, a fix plan, and a Preview test checklist for you to run before creating a version. Nothing in the container changes without your approval.