Sit rep…
It appears the issue was the PTFE tube routing immediately out of the AMS hub. A slight “off-straight” was enough to either make it slightly more awkward to push the filament through, or more likely in my eyes, interfere with the operation of the buffer arrangement.
I printed one of the suggested guides to ensure straight entry and exit of the PTFE though the hub and everything seems to work fine. I cannot replicate the issue.
Many thanks for all your help and ideas, it really is much appreciated. It’s great to have a supportive community like this, rather than some of the toxicity we see on other platforms. Hopefully I can help other users if they face the same issue. I guess it’s often the case where the solution is relatively simple and worth pursuing before you start spending money of replacement parts.
I’ll mark this issue as solved.
THanks again everyone, back up and running!!!
Gray