Before adding results into summary index, I can mvexpand a multi-value field as expected; for checking mvexpand search example,
... |table reason a |stats values(a) as a_list by reason |table reason a_list |collect index=test_index | mvexpand a_list |table reason a_list | ...
By stats, a_list has multi-value. The first table reason a and the last table reason a_list, though the field names are different (a va a_list), as a whole, the number of results and values are the same as expected.
But, when I tried to mvexpand to the results in the summary index,