Because SUP720-3BXL and because all who have a full BGP feed with it should have seen this in the last days:
*%MLSCEF-SP-4-FIB_EXCEPTION_THRESHOLD: Hardware CEF entry usage is at
95% capacity for IPv4 unicast protocol*
Because 512k routes should be enough for everyone (although the specs advertise 1024k).
Here you will find a workaround:
Ofc, reload is needed 🙁