Having bubbles coming out in a burst every 5 min is consistent with a very small leak. Usually this small bubbles will accumulate in a pipe bend until there is enough volume to be forced out in one shot.
My first approach would be to find the leak by elimination of possible causes, for example, are the bubbles coming out of all the OM outlets or just one or two?
does the pump makes a blending noise just before the bubbles come out?
You can also try using some silicone grease were ever there is o-rings joints, smotimes the o-rings don't seat properly and allow air to go in, if this is the case you would not see the salt creep for months.
The OM itself has an o-ring that needs to have silicone grease to seal properly, If it was not included with your unit, call Paul he will send you some.