leakage between nozzle and hot runner manifold.

Is the leakage between the machine nozzle connecting to the mold or is it internally in the hot runner ?

If it is internally then platen deflection can cause leakage especially if it is relying on thermal expansion to seal.

Paul.

As stated above but worth repeating

The nozzle radius and the manifolds radius MUST be the same.
The nozzle orifice should be smaller than the manifold by 1mm minimum.

NEW PLACES TO LOOK
Look at your machine - when the nozzle mates with the mold does it come in straight on? Or, does is jump up, down or sideways, when it touches? If this is the case your carriage-to-mold alignment is off. Fix the carriage

Examine the mold's HR bushing and the machine nozzle - are either/both dinged, chipped, or scratched? This could be your source of leaking. Re-machine the offender.

Watch the nozzle during the packing phase. Is this when it leaks? If it is your injection unit - carriage and all doesn't have enough force to create a seal.

During the injection phase, means there's a restriction in your hot runner system - You probably don't have an in-line filter on your nozzle and something (a chip of metal etc) is now in the hot runner. The only cure there is to disassemble it and clean it out. Purging won't work.

hope this helps.

please check your nozzle settings.
Zero position (KM) or "J" position (Engel)
Nozzle contact pressure.
If all this is OK, next:

do you have a cascade? are open during injection?

check nozzle radius and tool seat radius (nozzle must be smaler)

If it is OK, next:
hydraulics issue ... valve leakage

There are many types of HRs and so there are many possible reasons for this leakage. I would say that the best is to contact your HR supplier for assistance; they should support you, that's their job.

Anyhow independently of what kind of HR you have the reason for a leakage here is always the, steel to steel gap or mechanical failure.

There are 2 main different ways to make the sealing between the HR manifold and the housings: a by thermal expansion of the components or mechanically with threads.

If you have an HR which the nozzles are threaded to the manifold most likely you are facing mechanical failure somewhere. Even if it is a small fissure is enough to have resin going through.

If you have the option 2 then, most likely the expansion of the parts is not enough to seal between manifold and housing or you have too much high pressure on the system and this was not take into account during engineering.

May I ask you a couple of questions?
Who is the HR supplier?
Was this HR designed for this specific resin or you changed resin?
Do you have this issue since the beginning or it happened lately?
Was the HR designed for the mold and melt temperatures that you are using today?
Did you inspect the plates to see if they are as it should be?
Are you sure that the leakage is coming from there, how?
What's the max inj pressure? I don't know the resin but looking to the description I expect that it's quite viscous.
How many cavities you have and what's the distance between the most extreme ones?
Did you checked if the edges in contact between manifold and nozzle are sharp? They must be...