Install snapshot on Fritzbox 3390

I tried to install the snapshot on a Fritzbox 3390 and get this error using
I hope somebody can help me.

SETENV memsize 0x07ae4000 Traceback (most recent call last): File "./", line 40, in adam('SETENV memsize 0x%08x'%(addr)) File "./", line 33, in adam resp = ftp.sendcmd(cmd) File "/usr/lib/python3.7/", line 273, in sendcmd return self.getresp() File "/usr/lib/python3.7/", line 246, in getresp raise error_perm(resp) ftplib.error_perm: 500 'SETENV memsize 0x07ae4000': command not understood.