Attempting to display the Content Selectors in the Nexus UI resulted in an error:
Operation failed as server could not be contacted.
After increasing the request timeout in UI:Settings capability the content selectors could be displayed eventually.
Using the customer's system booted locally takes about 33 seconds for 455 content selectors to display. In their environment customer reports it takes a couple of minutes.
The problem was reported shortly after customer upgraded " our nexus version from 3.16 to 3.18, is there anything in the updating process that might have cause this issue?"
Worth also checking if this is a performance regression.