I'm having the same problem. Granted I don't have a cutting edge laptop, but it's and I7 with 8 GB ram running Windows 10 and the latest version of Designer. I'm using an XP-Pen 15.6 Pro. All the drivers are the most current available. I started a new file 16x20 @ 360 DPI. I placed a pixel sketch to use as a guide to ink the lines. I'm using the paint brush to draw lines. Everything runs smooth for about 10-15 minutes, and then I start to notice things gradually start to slow down. The brush begins to lag and slow down. I notice every time lines cross each other, icons for boolean operations keep toggling and Designer then begins to struggle keeping up with tasks. The more lines, the more it begins to slow down and then everything in Designer freezes and becomes unresponsive. Windows shows the program is not responding, and the application window turns light. I can alt tab out and Windows is responsive, web browsers and other programs work just fine while Designer is non-responsive. I go into the task manager and look at running programs and resources. Just normal Windows services are running, Affinity is utilizing the most resources, 2.5 gigs of Ram, 25% CPU, but the power usage is high. I end task and Designer instantly closes. I restart the program, load the recovery file and everything works just fine at normal speed, then gradually the whole process begins to repeat itself, have to end task and restart. Kind of mimics a memory leak and the program just loses resources. I thought it was the large file size, but I'm able to use the same file in Clip Studio, AI, and Photoshop. I've tried disabling the internet/network adapter, closing all unnecessary programs and services, disable the anti-virus and firewall and still encounter the same issue. I haven't tried drawing a low resolution image to rule out file size issues.
