Odd problem with disconnected filters still showing

Metabase 0.53.9
I've two idential tabs on my dashboard. Only difference is the way the date filters work - there are two date filters (actually just yyyy-mm and yyyy-qq).
I created the 2nd tab by duplicating the first (question by question), then disconnected the unwanted filter and connected the new filter.
I'm still seeing the unwanted filter on the 2nd tab even though it's not connected to anything. I've checked all the actions too. No linked filters either.
I've tested by putting nonsense values into the filters. They don't affect anything, so don't appear to be wired up.
Is this an odd bug or have I missed something? I'm trying to work out where these are stored in the database, but not obvious.

Fixed it. Maybe this will help someone else.

I found the id of the dashboard tab in

SELECT id, dashboard_id, name, "position", entity_id, created_at, updated_at
	FROM public.dashboard_tab;

that gave me tab 46 on dashboard 4
I then used

SELECT id, created_at, updated_at, size_x, size_y, "row", col, card_id, dashboard_id, parameter_mappings, visualization_settings, entity_id, action_id, dashboard_tab_id
	FROM public.report_dashboardcard where dashboard_id=4 and dashboard_tab_id = 46;

and looked through the parameter_mappings list.
In there, I could see two entries that related to the supposedly disconnected filters.
I changed the value of row for each entry to be a value greater than the last item on the dashboard tab (50 & 55 in this case).
That moved the faulty text items to the bottom of the dashboard from where I could easily delete them, then recreate.
For teh record, there was no filter mapped to either item. I could probably have just editing the parameter_mappings but was wary of breaking something.
Oddly, neither of the two text items was connected to a filter in the initial tab. The connection had been deleted previously. Looks like that was where the problem came from rather than the actual copying across.

Andrew - this is really interesting. I spent some time trying to replicate this behavior but I haven't been able to get to it. Can you clarify what you're referring to when you say "text items"? I assumed you meant text Cards that displayed filter selections but I wanted to confirm.

Yes, it's a text card.
The original tab had the card with filter connected. I removed the filter from the card. Then, when I copied, it still had the link to the filter in the report_dashboardcard table, but nothing visible in the dashboard.