Tee filter loses statements if branch target is slower

When we are running our simple insert test or our a bit more complex mixed test (SIUD) at a very high pace (10 us delay between statements) maxscale is not sending all statements to the tee'd instance after a short time.
When we lower the pace to 10 ms delay this does not happen.
Unfortunately maxscale is not throwing any warning or error (in maxscale error log) to make us aware of this.
This means tee filter cannot be used reliably in production.
Possibly a statement cache or something like this is overflowing?
Would be good to have something like a "synchronous" mode to guarantee that statements have been received my both database backends with possibly some timeout (similar to semi-synchronous replication).
We want to use this for some kind of quality assurance between 2 different backends and/or for doing a push replication from the secure to the insecure network zone in a security sensitive environment.