If you are ever attempting to add two lpm keys like “10.1.1.1/24” and “10.1.1.2/24”, those are actually both the same as “10.1.1.0/24”, and thus duplicate keys, which P4Runtime API does not allow.
I do not know if that is occurring in your case, but your mention that changing the prefix length from 24 to 32 caused the error to go away makes it possible.