Wrong order status set after PayPal payment received

[flix]

Hi there

I observed a strange behaviour of my Zen Cart:

Usually order status is automatically set to 'Payment received' whenever someone buys a product and successfully pays via PayPal. I then ship the product to the client and manually change the order status to 'Product sent to client'.
But sometimes (like once every 200 times), the order status is automatically set to 'Product sent to client' by Zen Cart after having received the PayPal payment without me doing anything manually. -> The result obviously is that I think that the order is already sent (despite the fact that it is not sent of course) and the client complains that he did not receive the payed product.

=> Has anyone also seen this strange behavior?

Any kind of input is highly welcome!

Regards,
Flix

[DrByte]

Neither of those order status names exist in original Zen Cart.

Assume I have a blank fresh new install of Zen Cart: now what do I have to do to my site to make mine function exactly as yours does?
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