Grafana loosing query parameters!

t=2020-10-27T17:15:11+0000 lvl=info msg="Proxying incoming request" logger=data-proxy-log userid=1 orgid=1 username=admin datasource=prometheus uri=/api/datasources/proxy/2/api/v1/query method=GET body=
t=2020-10-27T17:15:11+0000 lvl=info msg="Request Completed" logger=context userId=1 orgId=1 uname=admin method=GET path=/api/datasources/proxy/2/api/v1/query status=400 remote_addr=<remote> time_ms=2 size=127 referer=http://<host>/grafana/datasources/edit/2/

Can somebody help with it?
Was trying grafana:7.2.0 and grafana:7.1.5

prometheus connection settings: