Custom Admin Plugin – Injecting repeatable select fields (add, remove) into an Ordered List

A form is not allowed to be a child element of a table, tbody or tr.
Attempting to put one there will tend to cause the browser to move the
form to it appears after the table (while leaving its contents — table
rows, table cells, inputs, etc — behind).

You can have an entire table inside a form. You can have a form inside
a table cell. You cannot have part of a table inside a form.

Use one form around the entire table. Then either use the clicked
submit button to determine which row to process (to be quick) or
process every row (allowing bulk updates).

Read more here.