Steps to reproduce:

1) Download attached project 'unity.zip' and open in Unity
2) In Player Settings, make sure that Scripting Backend is set to Mono2x
3) Build and Run 'BugScene' on a device

Expected result: DllImported function with Mono2x should receive passed parameters just like IL2CPP (check attached image 'IL2CPP.png')
Actual result: DllImported function with Mono2x doesn't receive passed parameters (check attached image 'Mono2x.png')

Reproduced with:
5.4.5p2, 5.5.3p4, 5.6.1p1, 2017.1.0b7, 2017.2.0a1

Devices under test:
Samsung SM G950F, OS:7.0, CPU:arm64-v8a, GPU:Mali-G71, Build:samsung/dreamltexx/dreamlte:7.0/NRD90M/G950FXXU1AQDG:user/release-keys

HUAWEI EVA L19, OS:7.0, CPU:arm64-v8a, GPU:Mali-T880, Build:HUAWEI/EVA-L19/HWEVA:6.0/HUAWEIEVA-L19/C432B182:user/release-keys

Note: built project with IL2CPP receives passed parameters on both tested devices
Mono crashes on iOS. Tested with 5.4, 5.5, 5.6.