Setup of work order parent projects
The performance issue with opening EAM projects is related to the setup of work order parent projects.
Presumably, you have been using the same parent project since the beginning.
However, opening the main project takes a lot of time and is mostly useless.
Unfortunately, we have no easy fix for this but we can recommend setting up a new main project for work orders, so that accessing future work order projects is possible.
You can add a new setup line in the form [Enterprise asset management > Setup > Work orders > Project Setup:
Clicking edit and setting up a new project you should be good to GO.
It is difficult to have a precise recommendation for how often a new parent project is needed. A quick guess would be twice a year, but it all depends on the amount of work order projects are made.