Cant append FTP file with sim800c,only create

[Nikolay_Nikolay]

Hello, i am using Arduino nano and sim800c gsm module. I have a free ftp server i found on the interent. I am using terminal to check if ftp is working. The point is, for some reason, i can only create file on ftp server and write to it, i cant append it to add some data to the end of the file. So to create file i am using this AT comands.

AT+FTPCID=1

OK

AT+FTPSERV="185.253.34.65"

OK

AT+FTPUN="u202688_user"

OK

AT+FTPPW="*******"

OK

AT+FTPPUTNAME="privet.txt"

OK

AT+FTPPUTPATH="/"

OK

AT+FTPPUT=1

+FTPPUT: 1,1,1360

AT+FTPPUT=2,50

+FTPPUT: 2,50

I wrote this text and this is working well for me_

OK

+FTPPUT: 1,1,1360

AT+FTPPUT=2,0

OK

So after this commands i can see the file "privet.txt" with content "I wrote this text and this is working well for me_"

But if i want to append it it returns 71 erorr (operate error according to the datasheet)

AT+FTPPUTOPT="APPE"

OK

AT+FTPPUT=1

OK

+FTPPUT: 1,77

This error only appears when the file exists, so flag "APPE" does not work. If i delete file "privet.txt", it just creates a new file and writes to it. So i don't quite like the option of writing to the file only ones, i would like to append it mylityple times before it is big enough and i can create a new one. I didn't find the same mistake anywhere on the internet. Can anyone tell me where the problem can be?