According to the PMBOK Guide, a project manager should proactively engage with stakeholders to identify and resolve issues that may impact the project's objectives, scope, schedule, cost, quality, resources, or risks.
In this scenario, the project manager faces a bottleneck in the release management process, which may delay the delivery of the joint application development module and affect the integration with other modules.
Therefore, the best option is to speak to the stakeholders, such as the sponsor, the customer, the release manager, and the development team, to resolve the bottleneck and see how the entire process can be streamlined. This way, the project manager can ensure that the project delivers value to the customer and meets the expectations of the management. Pushing the team to deliver more, working toward the tighter deadline, or slowing the current pace are not effective options, as they may compromise the quality, scope, or alignment of the project. References: PMBOK Guide, 7th edition, pages 95-96, 101-102, 105-106.