The warnings have always been there, somewhat hidden in /var/log/pihole.log, a recent addition just made them more visible by also printing them into /var/log/pihole-FTL.log and showing them on the dashboard:
https://github.com/pi-hole/FTL/pull/1243
I don't think rising the limit will help. If an upstream server has issues to respond to queries and there are more than 150 queries awaiting reply from the server, this rather suggests something is wrong with your upstream server.
Please have a look into your /var/log/pihole.log file and look for said
Maximum number of concurrent DNS queries reached (max: 150)
messages.
Questions:
- What query happened exactly above?
- Is it the same domain that is queried very often?
- If 2 is yes: Did the upstream server this was sent to reply a single time for such a query?