CloudWatch Query Limit

Is there a limit to the number of AWS CloudWatch queries that can be added to a panel?
I created a panel based on the flowcharting plugin and added 6 queries and everything was OK, but when I added the 7th I got no results returned.
I changed the panel visualisation to a standard chart and still no results were returned.
When I deleted the 7th query all the results came back again.

For any one interested, it seems I’ve hit an AWS limit.
I’m using search expressions and the limit is 5 in one graph.

Search Expression Limits
The maximum search expression query size is 1024 characters. You can have as many as five search expressions on one graph