Merge Left Outer expansion removes rows

[lunchtime]

I spent good 90 minutes reviewing this
I am merging two tables. Source data comes locally and from sharepoint
I was doing a merge left outer and expanding and notice some rows were removed AFTER the expansion. In theory nothing should be removed
After some time researching on copilot this fixed it:
1. Option 1: Add between merge and expand
Table.AddColumn(
#"Merged Queries",
"MatchCount",
each Table.RowCount([tablename])
)
2. Option2: Buffer merge
#"Buffered Merge" =
Table.TransformColumns(
#"Merged Queries",
{ "tablename", each Table.Buffer(_), type table }
)

Note that this is not that it returned "null", the line simply dissapear until I used one of above
I have no idea why this happens, never happened before that I noticed. If anybody can explain that will be great
If others are banging their head maybe this can help you

 

[Chihiro]

Without knowing your data hard to say...
But in most cases, it's there, just not present in data preview. If it is actually missing from the end result (i.e. validated in data model or in returned table). Check your data types, filtering etc.