DIAGNOSIS: The router's web interface is resource-intensive, and this is a common complaint with older firmware or when using an underpowered browser. The router itself is probably working fine—it's just the admin panel struggling.
FIX: 1) First, try a different web browser. Chrome and Edge tend to work best; avoid Safari or older Firefox versions. 2) Clear your browser's cache and cookies. 3) Make sure you're not running a ton of other tabs, especially ones playing video. 4) Update the router's firmware. Go to 'Settings' > 'Administration' > 'Firmware Update' and check for an update. A newer version often has performance fixes.
IF THAT DIDN'T WORK: Try accessing the interface from a different device, like a phone or another computer, to see if the problem is isolated to your main PC. Also, a power cycle (unplug for 30 seconds) can clear up temporary memory issues on the router.
HEADS UP: Don't leave the DumaOS tab open for days on end. It can memory leak and slow to a crawl. Close it when you're done making changes. The laggy interface doesn't mean your internet connection or gaming traffic is affected.