Of course it does depend on what is open at the time....
The trouble is that clicking on the button is producing events and these events can overlap each other (re-entrance). So if you click the button for times in a row, your function can start running AGAIN before the first instance has finished, so if the table were opened exclusively in the first instance of the function, to try to open it again (in the second instance) produces an error.

Click slower, and you only ever have one instance at a time.

>>It depends on what else is open at the time.
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>Come on, it doesn't depend on anything.
>Moving from record 1234 to record 1235 is precisely the same, in my case, as moving from 1235 to 1236. All I do is move next, move previous, and if I do it quickly I get the error. It doesn’t matter the specific record, it may or may not happen on the same record, going up or going down…
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>dz