The test failures:
In file: findall
possible error in Goal: findall(A0,true,a)
Expected: [type_error(list,a)]
Extra Solutions found: []
Solutions Missing: [type_error(list,a)]

In file: findall
possible error in Goal: findall(A0,true,a / 3)
Expected: [type_error(list,a / 3)]
Extra Solutions found: []
Solutions Missing: [type_error(list,a / 3)]

In file: findall
possible error in Goal: findall(A0,true,foo(a,b))
Expected: [type_error(list,foo(a,b))]
Extra Solutions found: []
Solutions Missing: [type_error(list,foo(a,b))]

Unfortunately fixing this bug is rather hard as the type_error is thrown. Unfortunately it is destroyed by backtracking in the higher level findall (another case of vairable.value = null overwriting something that was visible from elsewhere) see also the bug in arg.