My configuration is: Windows 10 Pro v 1903 QGIS 3.10.0
I'm trying to load a specific composer layout model, but it not respond properly, slowing down my computer, consuming all it's memory, to the the point of giving me no option but a Windows hard reset. I've used this layout model in previous versions whit no problems at all. Also, creating a new blank layout work's just fine. I've try to overcome this situation by making a copy of a project that had already the layout in the composer manager, and, then, just adapt the layers and features. It was possible to open the layout and work on it, but when I'd saved the project, close the composer, and try to re-open, I've got the same memory usage issue.