Yes, fully agree with you, water shoud be mixed with corrosion prevention liquid . Usually yes, need only 1-1,5bar i saw it the in manuals as...
In my circulation line(fresh water) 3 bar (should be not less then 1,5bar) on 2 bar it will work stable, but ideally need 3 bar.
Check t.sensor in/out water . due to incorrect measurement of temperature your pcb keep compressors On untill antifreeze alarm.(water t.sensors...
