Order status changing unexpectedly - IPN issue?

Hi. We have an issue with orders apparently changing status randomly on version 2.3.0.2. We use the default template with styling changes and 5 or 6 modules. Essentially orders appear to set back to complete after they've been set to shipped - meaning they can get shipped again. Not good!
I'm wondering if this is anything to do with delayed IPNs - payment is via PayPal. We have seen this type of behaviour on other carts and whilst PayPal claim that IPN is 100% robust, experience suggests otherwise.
Has anyone seen behaviour like this please and if so, what was it and is there a published fix?
Thanks
Vanessa

VanessaJones wrote: ↑

Fri May 19, 2017 12:15 am

...
I'm wondering if this is anything to do with delayed IPNs - payment is via PayPal. ...
Thanks
Vanessa

You could check your server access logs to find out whether paypal IPN call backs are indeed responsible for changing the order status.