If NSX precheck is executed from SDDC-M in quick succession (less than 5-10 mins between 2 precheck invocation), 2nd precheck fails with error "NSX planning phase precheck - Resource validations timed out - please contact Broadcom Technical Support”".
VMware Cloud Foundation 9.1
This is due to first precheck on NSX returns success before repo sync is complete on NSX side.
If the second precheck fails, customer should try again and subsequent prechecks should pass.
Upgrade from 9.0.x to 9.1, can hit this issue