I can definitely understand how frustrating this may be. If restarting the Samsung Notes app does not work, it may need a quick reboot of your Samsung Galaxy phone or tablet device. Exit all running apps on your Samsung device. Power your device off and wait for a few minutes. Then, restart it and relaunch the Samsung Notes app. Next, you may have missed out on important updates to your Samsung Notes app. Go to the Google Play Store or Galaxy Store and look for Samsung Notes. Check if there are available updates, then download and install them. After this, you can try clearing the cache of the Notes app. If it still doesn't work, you can try disabling sync on your Samsung Cloud. Open the Settings menu of your Samsung device. Navigate to Accounts and backup. Select Samsung Cloud. Tap Synced Apps. Go to the Samsung Notes section. Next to Sync On, toggle the button to Off. Hope this helps.
This happened to me for a month now. Super frustrating. I haven't been writing comfortably ever since I updated my S6 lite. Samsung Notes keep crashing whenever I use the writing pad feature.
Been there done that, nothing seems to fix this bug.
P.S. I didn't lose my notes since I backed them up on the Samsung cloud but sadly the problem persists.