I have another theory about this: in 21.2 TFP made a slot lock, which by default has a value of 45 (a value of 45 is very suspicious 😄).
I can’t check, but in 21.1 this line was not in the code ( in full confidence )
<combobox depth="3" name="cbxLockedSlots" pos="105,-7" width="100" height="30" tooltip_key="xuiStashLockedSlots" type="ComboBoxInt" value_min="0" value_max="45" value_wrap="true" value_increment="1" />
Accordingly: mods versions BEFORE 21.2 simply do not have such a parameter and I suspect that this is the problem.
In the meantime, for my work on the interface, I replaced the value 45 with the one I needed... Will see what comes of this...