join rows step - after changing the steps on incoming hops, step gets into undefined / not working state

1. create new transformation
2. create data grid step with 2 string field; field1 and field2 and data rows 1,1 and 2,2
3. create second data grid step with 2 string field; field1 and field3 and data rows 1,a and 2,b
4. create select values step after each data grid step and select all fields
5. create join rows step and connect both select values steps. configure condition as field1 = field1
6. preview join rows step

field1	field3	field1_1	field2
1	a	1	1
1	a	2	2
2	b	1	1
2	b	2	2

note, you cannot select field1_1 in the join row condition

7. alter second select value step: rename field1 into field1b
8. alter condition in join rows step to field1 = field1b
9. preview join rows step

field1b	field3	field1	field2
1	a	1	1
1	a	2	2
2	b	1	1
2	b	2	2

10. save and close the transformation
11. open the transformation
12. preview join rows step

field1b	field3	field1	field2
1	a	1	1
2	b	2	2

So now the output is correct.

I've noticed this before: when you change something (metadata) on the
incoming steps of a join rows step, the output is unpredictable!
Above steps confirms it in a very simple situation.