I'm getting "identical instances" error for one mullion. But when I delete mullion selected in screenshot there is nothing underneath it.
When I select by ID and try to select the other one (1554133), ribbon changes as if something is selected, but nothing is shown and zooming to selected zooms to entire building.
File attached.
Revit is just being fussy. Happens from time to time. All's I did was fidget with it. Nothing special. Just patience.
@barthbradley wrote:All's I did was fidget with it
I tried that already, but couldn't solve it. Tried deleting that mullion and placing a new one, tried deleting all on the gridline and placing new one, tried toggling mullion join on / off for that mullion and those above and below it, nothing worked.
How did you solve it?
I've seen this warning on many projects. Usually the underlying cause is an extra curtain grid in nearly the exact same location. That happens when a curtain grid pattern has required a grid in a specific location but a user adds another one and during the course of editing people lose track of which are "required" by the property settings and those that have been added. It also happens when people add another grid instead of using Add/Remove Segments to change which segments are visible.
It also happens when there are two curtain walls in the same place (copy/paste culprit).
In your file it looks to me that the grids that are very close to the corner mullion are creating very small panels which would technically not be required and they are hidden by the corner mullion anyway. As mentioned in the other reply it is possible to eliminate this warning in your file by selecting all the corner mullions on the grid and placing them again.
Steve Stafford
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Hi @blank...
Thanks a lot for posting your question to the forums! Have the solutions suggested by @barthbradley @SteveKStafford helped with your issue?
We look forward to hearing back from you with more information so we can help you as a community!

Jonathan Hand
Industry Community Manager | AEC (Architecture & Building)
@handjonathan wrote:Thanks a lot for posting your question to the forums! Have the solutions suggested by @barthbradley@SteveKStaffordhelped with your issue?
No, tried fiddling with it in all ways, deleting it, replacing all on gridline, but nothing helped.
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