If I quit Neovim's containing terminal without exiting Vim first, then the next time I run Neovim I get the error:
E575: Error while reading ShaDa file: mark entry at position 2957 has Press ENTER or type command to continue
I want to not see this error on startup.
To reproduce this error run
nvim --cmd term exit the terminal while still in vim and then run
nvim --cmd term again. This error is caused by not exiting vim before closing the terminal.
:h E575and the error message you have corrupted data in your shada file. I'm not familiar with neovim but
:h shada-file-nameseems to indicate where is your shada file. So find your shada file, find the corrupted data and no more "unavoidable error"