Nothing wrong with that logic except it would appear only very small numbers, compared to total subscribers are being affected?
They don't terminate lines but going on our earlier assumption, they might well be terminating tunnels. Tunnel creation is probably a CPU as opposed to ASIC operation?
Tunnel creation or numbering of those tunnels or something equally inane could be the culprit. Or perhaps every 19th tunnel is having MSS/RWIN clamped. Or something is screwing with packet checksums or TCP sequencing so more packets in a flow are being examined under some undetermined circumstance. Or some other weird bug.
My limited experience of juniper is that they outperform cisco and are waay cheaper but documentation is sparse and bugs far more common than you'd like. TAC wants to investigate the bug you've reported? Cool. Where shall I put these 40k subscribers?
I bet PN support are looking at standard peak time load and under-utilisation with WTF style faces. ptn-ag2 was always flawless for me, if that helps.
Could be classic congestion and they're telling us porkies, though.