When applying a patch to Magento it is highly recommended to perform a complete site backup and investigate any known issues with the patch beforehand.
Magento patches have been known to be the cause of various errors and can interrupt both site function and integration. These errors in your Magento integration can cause it to no longer correctly communicate with Channels.
Problems can include:
- Incorrect Permissions
- Bad Data
- Blocked Access to Data
- Bad Service Logins
Patch SUPEE-7405 was known to cause problems with the SOAP API, was incompatible with PHP 5.3, and changed file and directory permissions among other problems.
As of February 23rd 2016, a patch update has resolved the problems with SUPEE-7405.
If you have questions about a patch before applying it, please feel free to contact the Support Team at your Magento Host.