No rows (also no errors) returned for valid queries

Dear all,
from time to time I won’t get any returned rows for a query that’s valid. It works perfectly fine, if I execute it via SSMS.
When I execute the query via Redash, I don’t receive an error message, but also no results. This usually happens when I have a couple of subqueries or multiple parameters. As soon as I split the the query in parts, it starts returning rows again.
We use 12GB RAM for our Redash app and we never received any out-of-memory notifications.

Are there any limitations on executing queries? Do you have any idea why this happens?

Thanks in advance
Leon