I am currently working on project, where I need to digitise a geomorphological map. I am working in ArcMap 10.5.1. I have an issue with creating new features. When I am digitising an object from the map sometimes, a strange error occurs with the geometry. It looks like after drawing some vertices, something's going wrong, and it seems like ArcMap on its own finished part of the sketch and closed the part of the polygon in very strange way. Here's the example:
When I was trying to fix the polygon manually with Edit vertices tool, it didn't worked well, because those long random lines are intersecting the part I have already created and geometry gets really complicated, so it's usually impossible to fix it manually. What's more interesting, during editing the veritices I have realised that the beginning vertex (which is indicated in ArcMap as red) have changed it's location, and now different vertex is indicated that way. Below here is example - I have indicated with yellow arrow the original position of begining vertex.
Sometimes, ArcMap is not "finishing part on its own", but those strange lines appear. Also, what's important it doesn't appear with every new feature I am creating, but it is often repeating in the same places of the map (e.g. I was trying to draw a new feature in the same place, when last time this error occured, and it occured again). I have been looking for similar problem, but I haven't found any. I also have tried the classical solution with reinstalling the software but it didn't work. Any ideas what can cause such problem?