Scepter bug?
Clones will replace other clones if one is available, but if you have three phantasms summoned, the oldest gets replaced.
^ Clone never replaces a phantasm.
EDIT: I tried this, it didn’t happen to me.
What Loafers says is correct. A Clone will always prioritize replacement of another clone when it is summoned, but if one is not available then it will shift to a Phantasm to ensure it spawns correctly.