I have the same experience with my profilux 3 ex,

apperently in my case the P3 seems to lockup ( at least the network part ) if I try to program the p3 via the network.

So I'm programming with PLC and I get a connection error ( don't know the code anymore ) , its not with every disconnect
but when I try to reconnect to the P3 (immediatly after disconnect ) and it doesn't work anymore.
Then I assume that the P3 is stuck ( the network part ) since the other functions of the P3 just continue,
another reason why I thing the network part is stuck is because I don't recieve my fixed timed emails anymore.

If I restart my P3 , everything is fine again. and I can connect with PLC and I recieve my emails again.
Since I know this (last week orso I realized I didn't get my mails after a PLC disconnect)
When I get disconnected from the P3 with PLC , I reconnect , to see if I can get a connection again or otherwise I'm never sure that I will get emails again.

I don't know if the plc connection can stay open on the while I loose connection to PLC.