The ABS accumulator.
As the member britlude reported, I thought about replacing the accumulator and pressure switch Assy from US as I think it is part of the ABS multiple issues.
However, after looking at the state of the ABS, I decided it is not cost effective to invest into this old/tired system.
There is no guarantee that it won’t fail in a few years time. Considering the state of the brake pipes and other ABS parts, we are now discussing about investing into the latest one body ABS module instead.