If this is a cloud environment the number of connections is limited by default. Creating pages with lots of selectors and grids might cause the connectionpool to run out of connections. This can be seen in the monitoring by looking at the connections graph and you’ll then see a graph with a flat top of the peak. Either find the page or function that is creating all these connections and redesign the page/function or ask via support to increase the number of possible connections. Keep in mind though that more connections will increase the load on de database, so more computing power (CPU and RAM) might be needed as well.

Locally you can change this in the configuration of your database (postgres.conf)