After you install March 2021 cumulative update for your Windows, you might have trouble printing to your printers. You might experience:
BSOD (Blue Screen of Death) with the stop error code APC_INDEX_MISMATCH for win32kfull.sys.
NiceLabel Designer, PowerForms, or Web Client freezes, then your computer restarts or shuts down.
NiceLabel Automation Service stops. Automation Manager throws an error: "Unhandled exception occurred while executing trigger: The operation completed successfully."
The error can occur in all Windows applications that use printer drivers. NiceLabel is just one of many affected applications.
Microsoft has already released new optional updates that correct the problem.
To apply a fix, do the following:
Install the March update (yes, the one causing the BSOD).
Install the "Out-of-band" update included in the "optional updates".
To access the optional updates, go to Windows Settings > Update&Security > View optional updates.
You might not see View optional updates link.In this case, click on the Check for updates button. If one or more optional updates are available, the View optional updates link will appear.
There are two updates you have to install. Each Windows version has different updates.
if you don't know your exact Windows version, you can check in Settings > System > About, or visit the Microsoft site.
You can also download and install the update manually by visiting Microsoft Update Catalog site and entering the appropriate KB number. Download the correct update that matches the version of your operating system. This solution works temporarily, only till the next automatic updates. If the next updates still don't fix the problem, you have to manually install the downloaded KBs again.
When the problem was initially detected, we recommended removing the March update. This solution works temporarily, only till the next updates. If the next updates still don't fix the problem, you have to remove the March update again.
If you are hesitant to install the new update, there is a step-by-step guide published by Microsoft on how to resolve the problem. It requires some technical re-configuration of each driver and Windows application you use for printing. See the instructions here and the video here.