All the command option tables in lftp.1 specify either their second or third column as lx, which all the versions of tbl/gtbl I have access to fail to recognize. This can be fixed by simply removing the x, but I'm not sure what you were trying to achieve with it--I haven't been able to find any tbl/gtbl documentation that describes that as a column specifier.
Here's an example of the error messages that result from trying to render the current manpage:
$ PAGER=cat man lftp >/dev/null
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:169: unrecognised format `<'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:169: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:188: `p' modifier must be followed by number
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:188: unrecognised format `h'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:188: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:218: unrecognised format `h'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:218: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:241: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:241: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:301: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:301: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:316: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:316: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:352: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:352: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:393: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:393: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:427: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:427: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:456: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:456: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:483: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:483: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:511: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:511: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:528: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:528: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:589: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:589: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:623: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:623: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:875: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:875: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:907: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:907: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:937: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:937: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:963: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:963: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:988: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:988: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:1046: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:1046: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:1068: unrecognised format `q'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:1068: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:1132: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:1132: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:1180: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:1180: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:1240: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:1240: giving up on this table
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:1518: unrecognised format `\'
/usr/bin/tbl:/usr/local/share/man/man1/lftp.1:1518: giving up on this table
$
All the command option tables in
lftp.1specify either their second or third column aslx, which all the versions oftbl/gtblI have access to fail to recognize. This can be fixed by simply removing thex, but I'm not sure what you were trying to achieve with it--I haven't been able to find anytbl/gtbldocumentation that describes that as a column specifier.Here's an example of the error messages that result from trying to render the current manpage: