The checksum error is the expected behavior when you try to execute a modified script from an existing instance, including a different version of a script referenced from a process icon. So this happens because your icon refers to a version of WBPP that is different (most likely older) than the current version.
To fix this, simply launch the Script tool (by double clicking the icon) and remove the MD5 checksum. Then you can execute the script without problems (e.g., by clicking Apply Global from the Script window).
Script checksums are a security enforcement feature. Scripts are potentially dangerous because they necessarily have to expose their source code. If something or someone modifies a script maliciously without your permission, really bad things could happen (no need to scare people by being more explicit, right?), since PixInsight's JavaScript runtime is extremely powerful (much more than a typical web browser for example).
The idea behind these MD5 checksums is simple: By forcing you to clear a code checksum before executing a script that is different from the original code that created a process icon, the responsibility for what happens next is entirely yours
In summary, if you try to execute a process icon and you get a checksum mismatch error, you should always ask yourself: has this script been changed by means of a recent update, of after installing a new version of PixInsight? If yes, and you clearly know it, then run it via Script by clearing the checksum. If not, then something strange is happening.
