I have a batch file attached to a group policy that is supposed to install an .msi. For some reason, when I apply the GP to the OU I want and restart said computers, the program will only install on some (not all) of the computers in the OU. The MSI in question is located on a network share that is accessible by all computers. I created a log export for the GP, compared it to the installs that work and I noticed two things:

1) Failed to grab execution mutex. System error 258
2) MainEngineThread is returning 1618

It looks like the 1618 is due to an application already running. How can I fix my group policy (or batch file) to resolve this issue? I'm just starting to work with batch files and any help would be greatly appreciated. 

Thanks!

Group policy can install MSI files natively without using a batch file. I would review this link and possibly test using GPO without the batch file.  It seems like from your errors that the install is trying to run while another MSI is already running.

First thing to try is to run the msi locally on a failed machine, does this install? check event logs for a workstation that doesnt install it should gleen some info.