Thanks for the detailed list of things to look at.
Please see my responses embedded below:
You say you are using 22.214.171.124. - did the problem exist before the upgrade?
*** We already had 126.96.36.199 installed and working fine with Authorize.net when we switched to PayPal. (Our non-profit is 29 years old, not sure how long we’ve been using Prestashop but it’s been a looooong time…)
Have you upgraded or installed any new modules?
*** Not since trying to use PayPal no. Only the different PayPal modules trying to find one that worked.
Did the issue start as soon as you installed the first Paypal module?
Why have you tried so many paypal modules?
*** We were trying to find a PayPal module that worked…
*** We had assumed it was a Module issue and not a Prestashop issue as we’ve never had this problem when using a different Payment Processor.
Have you checked for viruses etc on the server?
Are the duplicate orders created from the same shopping cart?
*** Yes. A random member renews their membership and sometimes it has 2 or 3 duplicates seconds apart. Oh, and sometimes it’s a webinar or other product, it’s not just the membership orders.
Check the server files to see date / time stamps to see if anything else has changed (malware)
*** Nothing that I can see.
Have you created orders yourself with the same results
*** No. We’re unable to duplicate in our tests. Looks to be random.
Have you cleared all cached or better still turn them off for now
*** Yes. Tried that first. Caching is turned back on now as it made no difference.
I think it is a lot of troubleshooting in your system as it is unlikely to be a PayPal or Prestashop bug
*** No idea… But it was never an issue with Authourize.net.
URL for us to check ?
*** Our store is here: https://secure.sdiworld.org/store/en/
*** But I just disabled the PayPal module and reenabled Authorize.net. We’ve been trying to get this working correctly for weeks. This forum was my last hope…
*** We have our annual conference coming up and we can’t be triple charging people for it… They’re already pissed off for getting charged double for their membership fee…
*** We also have some Spiritual Journeys priced at $5K and if Prestashop tells PayPal to charge them $15K instead (3x$5K) it’s a real killer for us…
Any other payment modules installed?
*** Not enabled while PayPal was enabled but Authorize.net was “installed” and disabled.
Are you sure customers are not clicking more than once (perhaps because of slow page refresh)
*** Never seen it happen in the last 10 years of using Authorize.net.
*** Even now, they would have to click the purchase button two or three times within a second. The logs show these happening almost simultaneously.
*** One set
*** Another set
*** Nothing changed…
*** Disable Overrides was turned on. I turned it off to enable overrides and no change.
Does the issue happen with Ban wire/ check modules
*** We don’t use these payment methods.
Is the problem with certain currencies or all?
*** All. We had enabled USD, CAD & AUD. Currently, only USD is enabled as of a few minutes ago. Authorize.net can’t support multiple currencies so I switched them off.
*** Since making the change back to Authorize.net a few minutes ago we’ve had a few orders and no duplicate transactions. But now we’ve lost the ability to accept non US currencies… We need a better solution...
*** Historically, with Authorize.net, we only ever see one order in Prestashop for any given cart, never any duplicates.