Brake Master... Truly independent circuits?

[skidd]

In a functioning brake system , are the front and rear fluid circuits truly independent? I ask, because it seems in my setup like fluid from one is finding its way into the other.

I have a '93 (edit, I had '95 here by mistake) cobra R master in front of a fox booster. I have a pair of aluminum reservoirs connected to each inlet independently. Also, I have an inline proportioning valve (aka pressure reducer valve) in the front circuit. The front brakes are plumbed to the end away from the booster, the rears to the end close to the booster. SN95 disks all around, with PBR fronts.

The brakes seem to be working just fine, stop strong and feel good.

I noticed about a month ago a bit of fluid seeping out the top vent ho!e in one of the reservoirs. I opened them up, and saw one was a bit high, the other a bit low. I didn't think much of it at the time and just leveled the fluid and walked away. I don't recall which circuit it was that was high.

About 2 weeks ago, it happened again. Got me thinking about how and why its happening. So, I've been googling for answers and finding nothing. Again forgot to pay attention to which circuit.

Today... Again. This time I took note, it was the rear circuit that was over-full. Wish I could say it has always been this one, but I just don't know. Truth is, I want to say it was the front last time. Just can't remember.

The master is a new one with only about 700 miles on the whole car.

Is fluid seeping between circuits inside the master somehow? If so, is it by design , or do I have a faulty master? Looking at the factory plastic master, I see the 2 inlets share the same reservoir, with an internal separator wall. This issue I'm having would be not a problem since the fluid would just spill over to the other side.

So, do I need to think about going with an OEM reservoir? Perhaps somehow link the 2 I have now? Do one-piece remote reservoirs have a similar separator to the OEM plastic ones? I was sure I've seen others with 2 completely independent reservoirs. Has anybody else seen anything like this?

Here is a look at he reservoirs during initial mockup.