If one part of the application needs to be changed frequently and/or is used by other applications, then it makes sense to separate it as a microservice. However, for other parts, I think it might be better to stay as a monolith since when you have a network in your calls, things get messier.

Networks are unreliable even if it is your local area network. In my career I saw some unrelated network equipment was sending a RST packet to load balancer with application servers IP address and resulting in service unavaiable errors. It took us weeks to find that out since it was happening very rarely and there were many layers between load balancer and application servers.

Network means slowness, connection errors, unknown results, etc all of which should be handled carefully.