Strange casts in fuzzed Spring tests, sometimes leading to compilation errors

[EgorkaKulikov]

Description

Run unit tests generation for PetController class in spring-petclinic application.
Use standard settings, just click OK on UI.

Actual behavior

The following test is generated (there are more than ten strange tests, this is just an example):

    @Test
    public void testProcessCreationFormByFuzzer1() {
        Owner ownerMock = mock(Owner.class);
        (((Owner) (doNothing()).when(ownerMock))).addPet(any());
        Pet petMock = mock(Pet.class);
        (when(petMock.getName())).thenReturn("duplicate");
        (when(petMock.isNew())).thenReturn(false);
        LocalDate localDateMock = mock(LocalDate.class);
        (when(localDateMock.isAfter(any()))).thenReturn(true);
        (when(petMock.getBirthDate())).thenReturn(localDateMock);
        BindingResult resultMock = mock(BindingResult.class);
        (((Errors) (doNothing()).when(resultMock))).rejectValue(any(), any());
        (when(resultMock.hasErrors())).thenReturn(true);
        ModelMap model = new ModelMap();
        OwnerRepository ownersMock = mock(OwnerRepository.class);
        PetController petController = new PetController(ownersMock);
        model.put(((Object) "abc"), ((Object) petController));

        String actual = petController.processCreationForm(ownerMock, petMock, resultMock, model);

        String expected = "pets/createOrUpdatePetForm";

        assertEquals(expected, actual);
    }

Note that there are two types of strange casts: to Object and to Owner/Errors. One of them leads to compilation error.

Additional context

Kirill says that this bug also reproduces on October release.

[EgorkaKulikov]

@IlyaMuravjov may be you now why does it happen?