Raspbian Jessie + mosquitto 'hangs'

[hoka]

Hi
i have been using:
Rasberry Pi B with Jessie installed and mosquitto MQTT for more than 6 months with everything working well until just recently when mosquitto apparently hangs
i say apparently hangs because i am not certain what is happening
i monitor the flow of messages using 2 different web pages on 2 different pc's to try to get a consensus of opinion from them.
at varying intervals (anything up to an hour) the message flow will stop for a short time (anything up to 2 minutes) and then continue with normal message flow.
this is important to me because each node sends a reference every 15 secs to show that the node is working ok
i do know that MQTT message delivery is not guaranteed but up until now everything has worked ok with 10 nodes communicating
i did recently edit mosquitto conf ans set max_inflight_messages 0, this made the interval before failure longer and leads me to think that my settings in the conf file might need adjusting. The conf file is unchanged other than adding the inflight messages line
as i am no expert with pi or mosquitto mqtt this problem has me mystified

thanks for any help
Dave

[hoka]

taking this further it looks like some sort of networking / setup problem
After restarting on pc the problem went away ??? however on the other pc even after switching off and restarting it still persists.
in every other respect the pc functions completely normally in other operations i.e. web access, talking to other pc's on the network

[hoka]

for anyone else 'suffering' from this problem
it turned out to be the pi system i dont know what exactly caused it but setting up a second pi with jessie & mosquitto the problem is resolved