This error appear with some SSH host :

The server response contains a null character at position 0x0000002A:

00000000 53 53 48 2D 32 2E 30 2D 4F 70 65 6E 53 53 48 5F SSH-2.0-OpenSSH_
00000010 37 2E 34 70 31 20 52 61 73 70 62 69 61 6E 2D 31 7.4p1 Raspbian-1
00000020 30 2B 64 65 62 39 75 37 0A 00 0+deb9u7..

A server must not send a null character before the Protocol Version Exchange is complete.

More information is available here:
https://tools.ietf.org/html/rfc4253#section-4.2

Null character can be part of the identification string ?