Please note that we've updated the Mount & Blade II: Bannerlord save file system which requires you to take certain steps in order for your save files to be compatible with e1.7.1 and any later updates. You can find the instructions here.
Can you upload the .txt document starting with "CrashUploader." (with a process ID) located at "C:\ProgramData\Mount and Blade II Bannerlord\logs" to upload.taleworlds.com? If there are more than one txt file starting with this, you can upload all of them. Please paste the link to this thread in the description box on the upload website so I can identify it.