To the best of my knowledge and readings, spiking fevers can occur with PMR. An persistent fever, however, would indicate a condition which should be investigated.

Ues. Mine came with a persistent low fever every afternoon

I believe that fever is the result
Of an immune system cranking up In response to something it is fighting - which could be some variety of inflammation including infection. Here’s a definitive explanation.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6047205/