I do not understand where on help.avenzamaps.com to reply so I reply here instead.
The placemark redraw is not noticeable until you have at least 70 placemarks.
On my Motorola X4 it is certainly happening, with AM 3.6.3. Should I update to 3.7 ?
When you have > 100 it begins to take time, with > 200 it begins to be too time-consuming.
My guess is that placemarks are written to an internal KML file, which needs to be re-read whenever updated.
I will also test if it happens on my iPhone 7.