s5 135U CPU928B and s7 CP340 communication 3964R procedure

Hi,
I am here for litle help, my communication program is working as far as 4 bytes send/receive.But more than 4 bytes plc stops sending.

Here s5 & S7 both the programs are attached.Communication between S5 and S7 is working very nicely with these programs, my problem is the length of data that I can send or receive is very limited , only 4 bytes. I want at least 18 bytes of to send/receive. I have Checked DX2 send/receive mailbox size(I put 1024words.When I changed the size ofsend-data 4 bytes to 8 bytes,s5 stop sending data to S7. Also same on s7 side when I changed the byte size 4 bytes to 8 bytes s7 stop sending data.

I think the program is very easy and as far as I know I am jumping or overlooking something that any of you may find that, please reply if you find something wrong.

Thanks