SSL_do_handshake() failed

I have this problem that looks like it comes from Nginx.
This is the Kong log:

SSL_do_handshake() failed (SSL: error:1408F10B:SSL routines:ssl3_get_record:wrong version number) while SSL handshaking to upstream

The cause of this error comes from the set_target function inside a plugin but I don’t know why

The strangest is that the server receives this:

code 400, message Bad request syntax ("\x16\x03\x01\x00½\x01\x00\x00¹\x03\x03<©\x1a/#ÏxnfvÉż\x9e\x97'¶FjAsÖ]\x80ϯ(\x9f\x96\x90nÿ\x00\x008À,À0\x00\x9f̨̩̪À+À/\x00\x9eÀ$À(\x00kÀ#À'\x00gÀ")                                                            Î" 400 -
 - - [23/May/2022 12:01:57] code 400, message Bad request version ("\x00\x008À,À0\x00\x9f̨̩̪À+À/\x00\x9eÀ$À(\x00kÀ#À'\x00gÀ")
 - - [23/May/2022 12:01:57] "½¹ó!ê©V³pÛ¾c²ÙÏ"Üón_