Customer is seeing lftp slowdowns with lftp-4.8.4-4.el8_10.x86_64 that go
away when they roll back to lftp-4.8.4-3.el8.x86_64. The version with the
issue was released in response to RHEL-88955, with no other changes
mentioned in the changelog. That said, the patch for this fix -
lftp-4.8.4-tls-close.patch - modifies buffer.cc as well as buffer_ssl.cc
and other files, so maybe something regressed.

In customer's words, "Following a dnf update overnight batch jobs using
lftp transfers are now taking hours rather than seconds."