Comment 98 for bug 93413

Try fooling with the value for --dpd-idle

  --dpd-idle <0,10-86400>
  DPD idle timeout (our side) <0,10-86400>
      Send DPD packet after not receiving anything for <idle> seconds.
      Use 0 to disable DPD completely (both ways).
    Default: 300

i.e.

In your config file have the line:

DPD idle timeout (our side) 0

(to disable it)