FreeBSD 10.1 can't "make -j5 buildworld" over NFS?

[J David]

On identical hardware, against the exact same NFS server, FreeBSD 9.3
can do a parallel buildworld, but FreeBSD 10.1 dies in cleandir with a
bunch of "stale NFS file handle" errors.

The mount options are the same on both clients:

192.168.20.161:/data/software/freebsd/releng-9.3/src /usr/src nfs
rw,tcp,nfsv3,noauto 0 0
192.168.20.161:/data/software/freebsd/releng-9.3/amd64/obj /usr/obj
nfs rw,tcp,nfsv3,noauto 0 0


192.168.20.161:/data/software/freebsd/releng-10.1/src /usr/src nfs
rw,tcp,nfsv3,noauto 0 0
192.168.20.161:/data/software/freebsd/releng-10.1/amd64/obj /usr/obj
nfs rw,tcp,nfsv3,noauto 0 0

FreeBSD 9.3 build output:

$ sudo make -j 5 buildworld
--------------------------------------------------------------
>>> World build started on Tue Apr 14 23:47:38 UTC 2015
--------------------------------------------------------------
[ ... time passes ... ]
--------------------------------------------------------------
>>> World build completed on Wed Apr 15 00:51:24 UTC 2015
--------------------------------------------------------------

FreeBSD 10.1 build output:

c$ sudo make -j 5 buildworld
--- buildworld ---
--- buildworld_prologue ---
--------------------------------------------------------------
>>> World build started on Wed Apr 15 01:01:09 UTC 2015
--------------------------------------------------------------
[ ... time passes ... ]
===> lib/libthr (cleandir)
--- usr.sbin.cleandir__D ---
--- cleandir_subdir_bhyve ---
===> usr.sbin/bhyve (cleandir)
--- usr.bin.cleandir__D ---
--- cleandir_subdir_gzip ---
===> usr.bin/gzip (cleandir)
--- usr.sbin.cleandir__D ---
--- cleanobj ---
--- share.cleandir__D ---
cat: .tmpfiles: Stale NFS file handle
bmake[6]: "/usr/src/share/i18n/esdb/Makefile.part" line 78: warning:
"cat .tmpfiles" returned non-zero status
--- usr.bin.cleandir__D ---
--- cleanobj ---
--- lib.cleandir__D ---
--- cleanobj ---
--- usr.bin.cleandir__D ---
--- cleandir_subdir_head ---
===> usr.bin/head (cleandir)
--- usr.sbin.cleandir__D ---
--- cleandir_subdir_bhyvectl ---
===> usr.sbin/bhyvectl (cleandir)
--- share.cleandir__D ---
--- clean ---
rm -f Big5-2003.esdb Big5-E.esdb Big5-ETen.esdb Big5-HKSCS.esdb
Big5-IBM.esdb Big5-Plus.esdb esdb.dir.BIG5 esdb.alias.BIG5  .tmpfiles
rm: Big5-2003.esdb: Stale NFS file handle
rm: Big5-E.esdb: Stale NFS file handle
rm: Big5-ETen.esdb: Stale NFS file handle
rm: Big5-HKSCS.esdb: Stale NFS file handle
rm: Big5-IBM.esdb: Stale NFS file handle
rm: Big5-Plus.esdb: Stale NFS file handle
rm: esdb.dir.BIG5: Stale NFS file handle
rm: esdb.alias.BIG5: Stale NFS file handle
rm: .tmpfiles: Stale NFS file handle
*** [clean] Error code 1

bmake[6]: stopped in /usr/src/share/i18n/esdb/BIG5
1 error

bmake[6]: stopped in /usr/src/share/i18n/esdb/BIG5
*** [_sub.cleandir] Error code 2

bmake[5]: stopped in /usr/src/share/i18n/esdb
--- usr.bin.cleandir__D ---
A failure has been detected in another branch of the parallel make

bmake[4]: stopped in /usr/src/usr.bin/head
*** [cleandir_subdir_head] Error code 2

bmake[3]: stopped in /usr/src/usr.bin
1 error

bmake[3]: stopped in /usr/src/usr.bin
*** [usr.bin.cleandir__D] Error code 2

bmake[2]: stopped in /usr/src
--- usr.sbin.cleandir__D ---
A failure has been detected in another branch of the parallel make

bmake[4]: stopped in /usr/src/usr.sbin/bhyvectl
*** [cleandir_subdir_bhyvectl] Error code 2

bmake[3]: stopped in /usr/src/usr.sbin
1 error

bmake[3]: stopped in /usr/src/usr.sbin
*** [usr.sbin.cleandir__D] Error code 2

bmake[2]: stopped in /usr/src
--- share.cleandir__D ---
1 error

bmake[5]: stopped in /usr/src/share/i18n/esdb
*** [_sub.cleandir] Error code 2

bmake[4]: stopped in /usr/src/share/i18n
1 error

bmake[4]: stopped in /usr/src/share/i18n
*** [_sub.cleandir] Error code 2

bmake[3]: stopped in /usr/src/share
1 error

bmake[3]: stopped in /usr/src/share
*** [share.cleandir__D] Error code 2

bmake[2]: stopped in /usr/src
--- lib.cleandir__D ---
A failure has been detected in another branch of the parallel make

bmake[4]: stopped in /usr/src/lib/libthr
*** [cleandir_subdir_libthr] Error code 2

bmake[3]: stopped in /usr/src/lib
1 error

bmake[3]: stopped in /usr/src/lib
*** [lib.cleandir__D] Error code 2

bmake[2]: stopped in /usr/src
4 errors

bmake[2]: stopped in /usr/src
*** [_cleanobj] Error code 2

bmake[1]: stopped in /usr/src
1 error

bmake[1]: stopped in /usr/src
*** [buildworld] Error code 2

make: stopped in /usr/src
1 error

make: stopped in /usr/src


What could be going wrong here?

Thanks for any advice!