We have observed more cases of lost trade or dsipute messages and found that the P2P network has peaks of load which is probably the reason that some broadcast messages do not arrive at all peers.
This can lead to the situation that you don’t receive the message from the peer when he started the payment or when he has received the payment.
That situation is likely worse if your computer was in standby more, specially if you are on a laptop and on battery as there are some restrictions for network resources applied by the operating system (we are investigating how to resolve those issues).
By restarting your application you have much higher chances to receive those missed messages from the seed nodes. So the advice for the next months until those iusses are fixed is to restart at least once a day or any time when you expect a message (trade takes already long and peer has not replied with confirmation).
Also update to todays v0.9.5 release asap as it comes with some minor improvements in that area.
We are working on several important fixes and they will be likely deployed with the next release, so the P2P network should be much more stable again after the majority of users have updated.