transfer results in broken files

uploading files via ftp with ssl results in broken files on the server. Filesize is multiple of 4k, but if files are larger thank 4k. Error Messages appear on both sides.

Client side:
ftp> debug
Debugging on (debug=1).
ftp> del img/SR305EB.png
---> DELE img/SR305EB.png
250 Delete operation successful.
ftp> put img/SR305EB.png
local: img/SR305EB.png remote: img/SR305EB.png
---> TYPE I
200 Switching to Binary mode.
---> PASV
227 Entering Passive Mode (88,198,38,22,198,54).
---> STOR img/SR305EB.png
150 Ok to send data.
===>START SSL connect on DATA
===>DONE SSL connect on DATA 7
426 Failure reading network stream.
44743 bytes sent in 0.00 secs (1040.7378 MB/s)
ftp> ls img/SR305EB.png
---> TYPE A
200 Switching to ASCII mode.
---> PASV
227 Entering Passive Mode (88,198,38,22,229,234).
---> LIST img/SR305EB.png
150 Here comes the directory listing.
===>START SSL connect on DATA
===>DONE SSL connect on DATA 6
-rw-r--r-- 1 1495 1495 16384 Nov 11 19:00 SR305EB.png
226 Directory send OK.
ftp> exit
---> QUIT
221 Goodbye.

Server Side:
Wed Nov 11 19:03:10 2020 [pid 16] [webxxxx] FAIL UPLOAD: Client "78.94.222.115", "/html/img/SR305EB.png", 16384 bytes, 96.56Kbyte/sec
Wed Nov 11 19:03:34 2020 [pid 15] [webxxxx] DEBUG: Client "78.94.222.115", "DATA connection terminated without SSL shutdown. Buggy client! Integrity of upload cannot be asserted."
Wed Nov 11 19:03:34 2020 [pid 16] [webxxxx] FAIL UPLOAD: Client "78.94.222.115", "/html/img/SR305EB.png", 77 bytes, 0.71Kbyte/sec
Wed Nov 11 19:03:51 2020 [pid 16] [webxxxx] FAIL UPLOAD: Client "78.94.222.115", "/html/img/SR305EB.png", 16384 bytes, 131.88Kbyte/sec
Wed Nov 11 19:09:55 2020 [pid 15] [webxxxx] DEBUG: Client "78.94.222.115", "Control connection terminated without SSL shutdown."

If i use filezilla instead, it works as expected: Same files on client side and server side.

Description: Ubuntu 20.10
Release: 20.10

ftp-ssl:
  Installiert: 0.17.34+0.2-5
  Installationskandidat: 0.17.34+0.2-5
  Versionstabelle:
 *** 0.17.34+0.2-5 500
        500 http://ftp-stud.hs-esslingen.de/ubuntu groovy/universe amd64 Packages
        100 /var/lib/dpkg/status

Expected: file integrity with transport.
Instead: file integrity broken.