I can not solve the problem myself in Autocad 21.0.
I worked on the project for almost 2 weeks. My work seems to never be completed. After the emergency power failure, the project opens, the program tells me about the error: Unexpected increase in file size. I hope that someone has come across something similar and will help solve this problem more quickly. I ran out of ideas how to help myself.
From one of the sources about AutoCAD
Using dwg recovery command you can recover as much data as possible from AutoCAD files with DWG, DWT and DWS extension. This command can be used for files which are damaged to such an extent that it cant even be opened by AutoCAD.
Open a blank drawing and type RECOVER on command line press enter it will open file browser select drawing which is damaged and click open. AutoCAD will attempt to recover as much data as possible from that drawing and it will open recovered drawing in a new tab of same AutoCAD window.
Moreover, in case it isn't help to restore dwg. I usually use Google, I found following for your case