Unable install terraform version 0.11.14
Getting this error whenever we tried to install 0.11.14 : not sure why this issue happening.

Since it "Failed to create the file"... have you checked, that there is space on the directory/partition (/tmp) and/or the user has write permission?
It works for me and this does not look like a tfenv issue.
Yes, /tmp permision is 775. We resolved this by replacing the tfenv-install file with the older version
TFENV_ARCH=amd64 tfenv install 0.11.14
What is the difference between the non-working and working versions? Does your problem still exist with the latest master?