HDPE Bottle thread shearing

[DShaw7]

Hi all.
First post. Be kind!
What is causing thread of neck to basically sheer of HDPE bottle?

It is not all bottles but out of batch of 960, 95% are all faulty.
It is not overtightening of the spray nozzle - we have tested this. There has been no impact or external pressure down or sideways in transport.
Both nozzle and bottle come from same supplier.
You would be shocked to know the bottle supplier has run away from it - no fault with the bottle.

Any help from anyone with knowledge here would be enormous as the disposal cost of the liquid inside is considerable.

Cheers Darcy

 

[IRstuff]

You would be shocked to know the bottle supplier has run away from it - no fault with the bottle.

Of course not, but the problem lies there; if they didn't have problems before, then they changed something in their process. There's either been a composition change in their input material or a temperature change in the processing.