Normally Apache is configured like below thread. Note only versions prior to 2.4.8 need the ChainFile setting and after is deprecated (as rg305 noted)
You definitely would not use fullchain.pem in both the ...File and ...Chain settings but it doesn't look like you are (per SSL Checker site I linked earlier)
And, something seems not quite right with your config as you are sending the X1 root. That's not harmful except it is extra data transmitted that is not used.
Apache Config:
Cert Chain Issue
https://www.ssllabs.com/ssltest/analyze.html?d=vistaman.ftp.sh&hideResults=on