Grafana unified alerting math rule not working properly

I have this math expression that yields “NO DATA”:
($tagHistoryMin<$thresholdMin) || ($tagHistoryMax>$thresholdMax)
No error message.

if I remove either the left or the right half of the expression like:
The expression works fine.

If I change the expression to:
($tagHistoryMin<$thresholdMin) || (1==1)
It also yields data.

What’s going on?

Never mind, I found it.
The 2 parts of the equation “thresholdMin” and “thresholdMax” contained extra tags that made it impossible to join the resulting tables (at least, that’s what I think what was going on). I ticked “ignore unknown” in both queries and now it’s working…