I am assuming these are 404 errors then? Most likely it is some sort of negative SEO. Someone (most likely in Russia I find) probably has a website setup some where, with all these links which Google found and tried to visit. Happens to me all the time. Search for the directory on Google and you will probably find the page.
Google also sometimes find errors were there are none. A couple of months ago Google was finding 100's of buttons to close errors and content wider than the screen errors on one of my sites. The errors would rotate to different URLs, finding something wrong with a URL one day and the next it was fine.
I had not changed the templates. Using a number of different tools like Google Mobile Friendly Test I never found an issue. Eventually Google seemed to settle down and my error count went back to 0