Paypal Payments Standard Issue since start of April BAD_INPUT_ERROR

I am using nopCommerce version 3.3.

Nothing has changed at with my configuration for the last 2 years. For the last 10 days some customers are unable to pay with PayPal, they keep getting the following error

flowlogging_id=ee7d930919202&code=BAD_INPUT_ERROR

I have rung PayPal and they are saying that it is most probably to do with the following topic.
https://www.paypal-techsupport.com/

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My Payments Standard integration isn't processing transactions. What should I do?
                          
Issue
Transactions involving Website Payments Standard, PayPal Payments Standard, or HTML buttons aren't processing, resulting in an error message similar to the following:

Cause
As of March 29, 2017, PayPal has updated to a new, streamlined checkout experience:

Most integrations work with this new PayPal checkout automatically. However, some integrations have issues that cause the user experience to fail. Some of the most common reasons for failed validation checks are:
Passing currency symbols ("$", "£", etc.) or values other than integers (1, 2, 3, etc.) and decimal points (“.”) in the amount field. For example, "1234.50" is correct, but "$1,234.50" isn't allowed.
Passing country code values greater than two letters. For example, "FR" is correct, but "France" or "fr_FR" isn't allowed.
Passing more than 127 characters in the item_number field. For example, don't use the item_number field for "Note to Buyer" information.
Passing more than 64 characters in the option fields (on0, on1, etc.).
Passing duplicate empty parameters.
Passing address_override=1 without passing an address.

Example of the problem
Here are two simple buttons that redirect to a PayPal.com checkout:

   Problem button (results in error message)     Working button (redirects to working checkout)  

In the HTML code for these buttons, the only difference is the value of the “amount” field. The button on the left contains a “$” value, which isn't allowed in the numeric amount. This results in an error message.


Solution
This error may be occurring only for certain transactions. If you have many items for sale, only some of them may exceed character limitations or pass invalid values as part of the transactions. You may need to test all available options to identify which ones lead to an error message. Once you find the affected transactions, review the HTML Variables for PayPal Payments Standard to troubleshoot your integration.
The original author or web developer who created your page with PayPal checkout buttons may be the best person to investigate and resolve these problems. Please contact them if they're available.
If you use third-party shopping cart software, such as a hosted shopping cart or software that you installed on your web server, the developer of that software may need to correct a problem in their code. Contact your cart provider directly and have them review this guide.
For websites that use static HTML, examine your HTML directly to see if there are problems in the values being directed to PayPal. For example, in the following code, the value of the amount field is "$1,000.00," which contains invalid "," and "$" symbols. It should be updated to "1000.00."

<form action="https://www.paypal.com/cgi-bin/webscr" method="post" target="_blank">
   <input type="hidden" name="cmd" value="_xclick">
   <input type="hidden" name="business" value="PayPalMerchant@example.com">
   <input type="hidden" name="item_name" value="Widget">
   <input type="hidden" name="amount" value="$1,000.00"> <--Problem: Remove currency symbol and comma ("1000.00")
   <input type="hidden" name="currency_code" value="USD">
   <input type="submit" value="Old PayPal checkout">
</form>

For more complex websites, such as those that use JavaScript or server-side software before redirecting the customer to PayPal, you may need to log the variables sent to PayPal. You can do this in your own code, or you can try using a browser tool, such as Google Chrome. Here’s how:
Go to Developer Tools > Network, clear the log, and enable the Preserve Log option.
Click a page action that would redirect a customer from your site to PayPal.com. If this opens a second window, you may need to enable Preserve Log in that window and then go back and redo the same page action in the original window.
Once you have a list of events, look for the first event named webscr, select it, then check the section titled Form Data.
Note: For more help resolving this issue, visit our Merchant Integration Technical Support Community.

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I'm not sure where to start to fix this issue? Any help would be much appreciated.

Regards Michelle

What is your site URL? Do you experience it for all products or certain ones?

site is www.organicwine.com.au

Some payments are coming through ok it seems, and sometimes the "Retry Payment" works when the initial re-direct has hit the error.

I have managed to get the string it is posting as

cmd=_xclick&business=info%40organicwine.com.au+&item_name=Order%20Number%2021342&amount=289.00&

Could the "+" after the business be the problem, taking it out seems to work!

Hi Andrei,

That seems to have solved the problem.

I had a space character at the end of my "Business Email:" field in the PayPal Standard Plugin settings. It has been there for over 2 years and working fine. But with the recent updates to PayPal  streamlined checkout, obviously it was now causing problems.

Phew so relieved to have fixed it. Fingers crossed!

Hopefully this might help someone else.

You sir, saved my life. Thank you.

Had the space at the end the business email too (NOP 3.8).
You saved my day ! Thanks !