No such file or directory in pg_replslot

I don't know if this applies only to pglogical or logical decoding in
general. This is on a 9.6.10 provider running pglogical 2.2.0. Subscriber
has same versions. We had a replication delay situation this morning,
which I think may have been due to a really long transaction but I've yet
to verify that.

I disabled and re-enabled replication and at one point, this created an
error on start_replication_slot that the pid was already active.

Somehow replication got wedged and now even though replication appears to
be working, strace shows these kinds of errors continually:
open("pg_replslot/pgl_foo_providerb97b25d_foo336ddc1/xid-1248981532-lsn-C940-F4000000.snap",
O_RDONLY) = -1 ENOENT (No such file or directory)
open("pg_replslot/pgl_foo_providerb97b25d_foo336ddc1/xid-1248981532-lsn-C940-F5000000.snap",
O_RDONLY) = -1 ENOENT (No such file or directory)
open("pg_replslot/pgl_foo_providerb97b25d_foo336ddc1/xid-1248981532-lsn-C940-F6000000.snap",
O_RDONLY) = -1 ENOENT (No such file or directory)
open("pg_replslot/pgl_foo_providerb97b25d_foo336ddc1/xid-1248981532-lsn-C940-F7000000.snap",
O_RDONLY) = -1 ENOENT (No such file or directory)
open("pg_replslot/pgl_foo_providerb97b25d_foo336ddc1/xid-1248981532-lsn-C940-F8000000.snap",
O_RDONLY) = -1 ENOENT (No such file or directory)
open("pg_replslot/pgl_foo_providerb97b25d_foo336ddc1/xid-1248981532-lsn-C940-F9000000.snap",
O_RDONLY) = -1 ENOENT (No such file or directory)
open("pg_replslot/pgl_foo_providerb97b25d_foo336ddc1/xid-1248981532-lsn-C940-FA000000.snap",
O_RDONLY) = -1 ENOENT (No such file or directory)
open("pg_replslot/pgl_foo_providerb97b25d_foo336ddc1/xid-1248981532-lsn-C940-FB000000.snap",
O_RDONLY) = -1 ENOENT (No such file or directory)
open("pg_replslot/pgl_foo_providerb97b25d_foo336ddc1/xid-1248981532-lsn-C940-FC000000.snap",
O_RDONLY) = -1 ENOENT (No such file or directory)
open("pg_replslot/pgl_foo_providerb97b25d_foo336ddc1/xid-1248981532-lsn-C940-FD000000.snap",
O_RDONLY) = -1 ENOENT (No such file or directory)
open("pg_replslot/pgl_foo_providerb97b25d_foo336ddc1/xid-1248981532-lsn-C940-FE000000.snap",
O_RDONLY) = -1 ENOENT (No such file or directory)

Any suggestions? This is a showstopper for us.

Thank you,
Jeremy