panic: Duplicate free of 0xfffff8000445af10 from zone 0xfffff80004021000(16) slab 0xfffff8000445af90(241)

cpuid = 1
time = 22
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x47/frame 0xfffffe00269d56b0
vpanic() at vpanic+0x1e0/frame 0xfffffe00269d5710
panic() at panic+0x43/frame 0xfffffe00269d5770
uma_dbg_free() at uma_dbg_free+0x246/frame 0xfffffe00269d57c0
uma_zfree_arg() at uma_zfree_arg+0x1c1/frame 0xfffffe00269d5850
free() at free+0xed/frame 0xfffffe00269d5890
nfsrv_nfsuserdport() at nfsrv_nfsuserdport+0x1f9/frame 0xfffffe00269d58c0
nfssvc_nfscommon() at nfssvc_nfscommon+0x97f/frame 0xfffffe00269d5950
sys_nfssvc() at sys_nfssvc+0x133/frame 0xfffffe00269d5980
amd64_syscall() at amd64_syscall+0x436/frame 0xfffffe00269d5ab0
fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe00269d5ab0
--- syscall (155, FreeBSD ELF64, sys_nfssvc), rip = 0x2000028d, rsp = 0x7fffdfffdeb8, rbp = 0xa ---
KDB: enter: panic
[ thread pid 6974 tid 100340 ]
Stopped at      kdb_enter+0x6a: movq    $0,kdb_why