Jeep Hydroboost brake problem

I posted this over on pirate 4x4 got some good answers but nobody seemed to have a solid answer on my problem. Thought I'd post it over here and see if anybody's ever dealt with something like this.

I have a Scrambler which has a Vanco hydroboost in it. It has a PSC upgraded power steering pump, PSC reservoir along with a hydro assist Ram. It had an AMC 360 in it, it now an LS3 crate motor in it and the problem has continued from one motor to the next.

For years and years every once in awhile it feels like I lose the Hydro Boost pressure and the brakes go to manual feel on the pedal. It becomes very difficult to stop the Jeep. The Hydro Boost has been sent back to Vanco and rebuilt they have no clue what the problem is. The brakes have been bled multiple times we highly doubt there's any air in the system. Sometimes it'll do it multiple times in a row and then it'll go for days and not do it sometimes it'll go for months and not do it's very erratic. Oh when it does it the pedal has a very slow return. I have to lift up with it with my foot at times the last inch or so. Three or four years ago I change the master cylinder and that did not help either. Any idea what the hey the problem is?

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