Try it yourself: Create a full screenshoht from the product page of Instacap on Appsumo.
Now try to annotate. The complete long screenshot is shown at once.
Cons:
1️⃣ Click on the zoom-in icon and it enlarges the screenshot (with bad behavior) click on the zoom-out icon does not go a step back, instead it shows the complete screenshot again.
2️⃣ Use a pencil or rectancle (or any annotation tool). You can set it to the lowest width, it will show up huge.
3️⃣ Comments: Comment anywhere on the Screenshot. Go to the right sidebar and click on a comment, it will not show you the position on the screenshot (does not navigate to the point)
4️⃣ Support? I asked 2 days ago in my account about these bugs, no reply until today also no email. So I decided to write this here.

I have made a screencast of these bugs:
https://share.zight.com/8LueBGjN