proftpd stops randomly. Ideas anyone

i am having problems with proftpd stopping working - sometimes with a hung process which blocks restart - i have added a killall to the webmin monitoring but am looking to solve this issue - would it be possible to move it from stand alone to inetd without messing up the config - we ONLY use a single shared IP on this host.

Anyone else have this? (or something like it)

Operating system Ubuntu Linux 14.04.5
Webmin version 1.831
Virtualmin version 5.05
Theme version Authentic Theme 18.32
Kernel and CPU Linux 3.16.0-77-generic on x86_64
Processor information Intel® Xeon® CPU X5650 @ 2.67GHz, 8 cores

I found this:-

Which i have done, but i am still watching for repeats of the failure.