See https://reviews.freebsd.org/D21427 The diff is 160KB in size so I'm not attaching it, you can find it here: https://people.freebsd.org/~mjg/vop_unlock_complete3.diff There may be kernel modules failing. The patch applies cleanly on top of r351556.
New failure logs on i386: http://package23.nyi.freebsd.org/data/headi386PR240156-default/2019-08-28_21h59m47s/logs/errors/lsof-4.93.2_4,8.log http://package23.nyi.freebsd.org/data/headi386PR240156-default/2019-08-28_21h59m47s/logs/errors/open-vm-tools-10.3.0_1,2.log http://package23.nyi.freebsd.org/data/headi386PR240156-default/2019-08-28_21h59m47s/logs/errors/open-vm-tools-nox11-10.3.0_1,2.log http://package23.nyi.freebsd.org/data/headi386PR240156-default/2019-08-28_21h59m47s/logs/errors/openzfs-kmod-2019072200_1.log http://package23.nyi.freebsd.org/data/headi386PR240156-default/2019-08-28_21h59m47s/logs/errors/pefs-kmod-2018.11.26.log
On amd64 the failure logs are similar.
Sorted out, kernel change committed in r356337 .