The code snippet is already adjusted to jim mcnamara's suggestion, which unfortunately didn't solve the problem.
The error is caused by the ssh
-T and -t are doing the absolutely opposite thing.
Anyway, when I use -t, I only get another error.

Code:

Pseudo-terminal will not be allocated because stdin is not a terminal.

Which I can relate to.


Running every command for its own on the shell itself works perfectly, the codeblock itself also works as intended, I only get this error message from the ssh.
Running the ssh command on shell is also fine

Code:

# ssh -n -T hscroot@X.X.X.X "lshwres -r proc -m XXX --level sys -F 'configurable_sys_proc_units installed_sys_proc_units curr_avail_sys_proc_units'"; echo $?
16.0 16.0 10.0
0

EDIT:
IFS is set to single space, which also works fine.