Why is my replacement battery draining so fast?

Installed the replacement battery in my Galaxy S10+ about a week ago, following instructions. I fully charged it to 100% (plus 2 hrs) and let it die, then charged it again. Seemed to work well the first few days. But since then, it drains very fast. AccuBattery app tells me it drains about 20%/hr with screen on and ~10%/hr with screen off. I don't believe I use any heavy -draining apps; keep the screen fairly dim, don't watch many videos, etc. Any help is appreciated. Thank you.