There is a duplicate but it seems to have been deleted from Bugzilla.
I was provided with this patch:

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 30818b006530..f0a607c795ef 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4597,6 +4597,8 @@ static bool nfsd_breaker_owns_lease(struct file_lock
*fl)
       if (!i_am_nfsd())
               return NULL;
       rqst = kthread_data(current);
+       if (!rqst->rq_lease_breaker)
+               return NULL;
       clp = *(rqst->rq_lease_breaker);
       return dl->dl_stid.sc_client == clp;
}

     And it resolved the problem BUT as of 5.8.3 it is STILL not in the kernel.
This problem only gets triggered with a mix of NFSv3 and NFSv4 clients.