Comment 3 for bug 1580385

It really seems to be a problem inside lua-lpeg (0.12.2-1) found in Xenial, and seemed to have been fix (reading the upstream bug) in 1.0.0 found in Bionic and late.

Which also explain why when tried with Bionic the issue was not reproducible.

# rmadison
 lua-lpeg | 0.12.2-1 | xenial
 lua-lpeg | 1.0.0-2 | bionic/universe
 lua-lpeg | 1.0.0-2 | disco/universe
 lua-lpeg | 1.0.0-2 | eoan/universe

Reference:
http://lua.2524044.n2.nabble.com/LPeg-intermittent-stack-exhaustion-td7674831.html
https://github.com/nmap/nmap/pull/478