No graphical sub-ROM function working in MSX-DOS

I am trying to use the sub-ROM graphical functions, specially the BLTVD, but for any "BLT" one I always get a "Syntax error in 0" or "Type mismatch in 0" or things like that.

My code for calling is this:
Header:

typedef struct {
	byte a;
	word hl, de, bc;
	byte f;
} CpuRegisters;

Code. The calling convention is passing parameters in stack from left to right. The "callee" means the function itself restores the stack.

#define EXPTBL 0xFCC1
#define CALSLT 0x001C

; void call_bios(address routine_address, CpuRegisters *registers) __smallc __z88dkcallee;
public _call_bios
_call_bios:
	; extract values
	pop bc ; ret
	pop iy ; IY = *registers
	pop ix ; IX = routine_address
	push bc ; ret
	call load_regs
	push iy
	ld iy, (EXPTBL - 1)
	call CALSLT
	pop iy
	call save_regs
	ret

; void call_subrom(address routine_address, CpuRegisters *registers) __smallc __z88dk_callee;
; wrapper for calsub
public _call_subrom
_call_subrom:
	; extract values
	pop bc ; ret
	pop iy ; IY = *registers
	pop ix ; IX = routine_address
	push bc ; ret
	call load_regs
	push iy ; save *registers index
	call calsub
	; copy return values
	pop iy ; restore *registers index
	call save_regs
	ret

load_regs:
	; copy values to registers
	ld a, (iy)
	ld l, (iy + 1)
	ld h, (iy + 2)
	ld e, (iy + 3)
	ld d, (iy + 4)
	ld c, (iy + 5)
	ld b, (iy + 6)
	ret

save_regs:
	; copy registers to memory
	ld (iy), a
	ld (iy + 1), l
	ld (iy + 2), h
	ld (iy + 3), e
	ld (iy + 4), d
	ld (iy + 5), c
	ld (iy + 6), b
	push af ; save F
	pop bc
	ld (iy + 7), c
	ret

; CALSUB
;
; In: IX = address of routine in MSX2 SUBROM
;     AF, HL, DE, BC = parameters for the routine
;
; Out: AF, HL, DE, BC = depending on the routine
;
; Changes: IX, IY, AF', BC', DE', HL'
;
; Call MSX2 subrom from MSXDOS. Should work with all versions of MSXDOS.
;
; Notice: NMI hook will be changed. This should pose no problem as NMI is
; not supported on the MSX at all.
;
;#define CALSLT 0x001C
#define NMI 0x0066
#define EXTROM 0x015f
;#define EXPTBL 0xfcc1
#define H_NMI 0xfdd6
;
calsub:
		 exx
         ex     af,af'       ; store all registers
         ld     hl,EXTROM
         push   hl
         ld     hl,0xC300
         push   hl           ; push NOP ; JP EXTROM
         push   ix
         ld     hl,0x21DD
         push   hl           ; push LD IX,
         ld     hl,0x3333
         push   hl           ; push INC SP; INC SP
         ld     hl,0
         add    hl,sp        ; HL = offset of routine
         ld     a,0xC3
         ld     (H_NMI),a
         ld     (H_NMI+1),hl ; JP  in NMI hook
         ex     af,af'
         exx                 ; restore all registers
         ld     ix,NMI
         ld     iy,(EXPTBL-1)
         call   CALSLT      ; call NMI-hook via NMI entry in ROMBIOS
                             ; NMI-hook will call SUBROM
         exx
         ex     af,af'       ; store all returned registers
         ld     hl,10
         add    hl,sp
         ld     sp,hl        ; remove routine from stack
         ex     af,af'
         exx                 ; restore all returned registers
         ret

I think the parameters are located properly (many times I reverse them because the little/big Endian...).
Tested with many other BIOS and sub-ROM functions, and seems to work fine. Tested with:
- Functions without parameters, like INIPLT or TOTEXT.
- Functions with parameter in A, like CHGMOD or CHGMDP.
- Functions with parameter in HL, like NRDVRM.
- Functions reading parameters from RAM, like INITXT.
All works fine.
But any graphical one don't work, tested with:
NVBXLN, NVBXFL: does nothing.
BLTMD, BLTVD: the "Syntax error 0" message.
More interesting about getting that message because I change to SC5 (with CHGMOD) before using them, so don't know how it writes it.