We have a Windows Load Balancer, 2 WFE, 2 SharePoint Application Servers (one with Central Admin) and a SQL Server backend.
We are able to fully publish Nintex forms on one WFE but receive an error when hitting the other WFE.
Not sure if this is a Network Load Balancer (NLB) issue or an issue with the WFE talking to the Application Server.
Do you have any screenshots of the behavior you are seeing? Feel free to share and we can take a look! Off the top of my head, I would suggest navigating to Central Administration > System Settings > Manage Farm Solutions and ensure that the solutions deployed to that server properly.
Depending on the error, it may be necessary to pull the log file and see exactly what the feedback is when hitting the problematic WFE server. If you have a support entitlement with Nintex it would be best to contact firstname.lastname@example.org and have them review the log file and behavior to determine what is going on.