Three other things of note now that I have looked at your model.
The tilde in the file name means you are working on the backup file not the original, this leads to all sorts of problem the least of which is you will end up with multiple backup files with multiple tildes.
Your ‘terrain’ is upsidedown, meaning the back faces are up, so technically you are modeling it the wrong way around. Again this can cause issues, render engines often ignore anything on the back face, and 3d printers use the back face to know what is air and what is material.
You have Length Snapping enabled in Model info/Units, this can lead to inaccuracies when modelling and should be turned off by default. Experienced users make their own templates or modify the basic ones and turn that setting off and resave the template.