Try the instructions in the following link:
Log files and bug reports
You can actually help us improve the installer by sending us your log file when you encounter a problem during installation. Calamares makes a log file by default and you can retrieve it by copy-paste the following in the terminal:
xed /home/liveuser/endeavour-install.log
Or Pastebin it and show the URL in the forum:
cat /home/liveuser/endeavour-install.log | eos-sendlogs
This will upload the log to ix.io and create a short URL to the log file.
You could use the eos-sendlog tool and post the URL you will get.