It can be a fluke !
Just test it in 4 weeks again and see if there are any changes.
Make sure to use the same lab, but I am sure that you already know that.
Sometimes PSA can fluctuate even after RP, at least that is what our surgeon told us. Unfortunately my hunch proved to be more correct than his *sigh... BUT - my husband had so many unfavorable findings to begin with and he was gleason 9.
Not to mention that one node was glowing on the first PSMA and was dismissed by urologist and RO as "false positive".
Try not to panic but be proactive and keep checking uPSA every month until it stabilizes 👍.