This is likely to do with aarch64 on EL7 defaulting, against all sanity, to 64KB pages. Unfortunately, it is what it is.
AFAICT, it is directly related to this bug:
Unfortunately, that bug long postdates EL7, so a better, working jemalloc will likely need to be supplied.
MariaDB supplied jemalloc is the same as EL7 aarch64 EPEL jemalloc (same version, broken in the same way).