Source Google Sheets - Connection to Google Sheets fails when google sheets has a Data Connector to Big Query

Yes, that was my suspicion indeed. And yes, the name of the tab is “Connected sheet 2”.

And the output of the data (what I see on Google sheets at least), it’s just like a normal table:

id|name|address|
|A789|Test|test|
|A800|TEST|Teststr.|
|T001|Testmarkt 1|St.-Martin-Str. 72, 81541 München|
|T002|Testmarkt 2|Birkenleiten 43, 81543 München|