Steps to reproduce:
1) Create template T1.
2) Create item in T1.
3) Add preprocessing steps SNMP walk to JSON. (all available fields).
4) Create template T2.
5) Link T1 to T2.
6) Navigate to item in T2.
7) Open preprocessing tab and check SNMP walk to JSON step.

Result:
Remove and Add buttons are enabled. We can press them, visually we will see that preprocessing steps are removed/added. After pressing update button - success message appears. Check again preprocessing - everything ok, all steps exists.

Expected:
Remove and add buttons disabled.