2008 International Conquest Super C Brakes

[revoirfamily]

Hello to Everyone- New to Forum
Just recently purchased a 2008 Gulfstream 37’ Super C built on International 4200 chassis.
After about 400 or so miles the “low Brake Pressure light� illuminated along with illumination of ABS light on dash. Brakes felt fine; fearing a serious issue we stopped and turned unit off. After checking for leaking lines and master cylinder fluid levels we restarted the motor and lights were now OFF. This happened several more times. along with in the coach going into creeper mode where forward movement was strained and limited to about 10 MPH.
Summoned a service mechanic who arrived to coach and pulled the ABS sensors wiped them off and re-inserted. We travel another ways to area near Green view Tennessee where brake pressure completely disappeared at cruise speed and hand brake was only means of stopping.
Towed to local camp ground again summoned recommended service technicians who using a meter device informed we needed to replace the ABS sensors along with some solenoid under the master cylinder! Sadly they informed that since they were “rural� getting parts was an issue. We called a International dealer and had parts FEDEX to Camp ground overnight.
Next day service repair installed parts. Costs $350.00 for parts and shipping plus $150.00 to install. Finally around 6 PM we departed towards Maryland; no more than twenty miles later problem came up again. Service repairman again checked for “codes� in computer…We finally got to return to Maryland around 04:30 in the morning. We took Motorhome with lights illuminated to a International Truck dealer in Virginia after three days of diagnostic checking we were SHOCKED to learn the following
Parts we spent $500 on did not need to be replaced and the parts needed to fix problem are an electronic device with motors that controls the brakes and cost to replace will be $4848.00
I’m stuck as I already own it so I must repair it- but I’m hampered on question if this is a “Gulfstream Super C� issue- have other owners of similar models experienced similar braking issues?