I have two dataflows that have been working for months and still refresh successfully. The issue I have is that when editing either of them now, then clicking save and close, I get an error message saying 'An error occurred whilst validating your queries' after a few minutes. This even happens when making no changes at all to the existing data flow and just clicking 'Save and Close', suggesting that either...
the validation process has changed since this was last done successfully
there is a wider problem impacting both dataflows
I am able to see a preview of all tables before with no errors before clicking Save and Close so can't narrow it down to any issue with a particular table. This means I can't edit develop either data flow beyond their current state and seems too much of a coincedence that both are experiencing the same issue all of a sudden.
The fact this error occurs so quickly seems to suggest it isn't a memory issue.