From where are you importing the tab?
Same machine?
How are you exporting the code?
export with nodes selected or do you select tab after selecting export?
Also, if you exported a tab and import to current tab: it may be problematic.
(Had to think how to put that a few times as all I could ge twas local talk and that wouldn't translate too well.)
I think it depends how you exported. If you export "some" nodes then you can import to current flow, but if you export the complete flow (tab) it creates that same tab when you import.