Query Returns WRONG FIELD!!!

This is at least the 3rd time I've come across something that is, to me, an extremely serious bug in Access. Anyone else seen this, and anything I can do to avoid it??
In a query, I ask for the values from Field A.
The query returns the values from Field B, but still calls it Field A.

This is in a fairly complex query. If I delete one particular field from the query, the bug disappears. If I put that field back, the bug returns.

Here is my current query:
SELECT ByPN_1.PartNumber, ByPN_1.LostPerSetup, ByPN_1.ActualMachine, ByPN_1.PermQty, ByPN_1.FirstOfFeederSize, ByPN_1.Leaf1, ByPN_1.FirstOfType, ByPN_1.NonPerm, IIf([nonperm]*[concurrentsetups]<1,1,CLng([nonperm]*[concurrentsetups])) AS QtyIfDed, [nonperm]*[setupsperday] AS MaxLoadsSavedPerDay, [qtyifded]*[setupsperday]/[concurrentsetups] AS DedLoadsSavedPerDay, IIf([maxloadssavedperday]<[dedloadssavedperday],[maxloadssavedperday],[dedloadssavedperday]) AS LoadsSavedPerDay, [loadssavedperday]*[laborrate]*[loadunloadperfeeder]*250/60 AS Labor_Annual, master_attr.STD_COST, [loadssavedperday]*[lostpersetup]*[std_cost]*250 AS Parts_Annual
FROM (ByPN_1 LEFT JOIN FeederCost1 ON (ByPN_1.ActualMachine = FeederCost1.Machine) AND (ByPN_1.FirstOfFeederSize = FeederCost1.Size) AND (ByPN_1.FirstOfType = FeederCost1.Type)) LEFT JOIN master_attr ON ByPN_1.PartNumber = master_attr.ITEM
WHERE (((ByPN_1.PartNumber)=107573));

HEre's the pertinent part of the record from BYPN_1:
PartNumberLostPerSetupFirstOfFeederSize
107573 3 12X4

But here's what the query returns:
PartNumberLostPerSetupFirstOfFeederSize
107573 12X4 12X4

Now, if I just delete the "parts_annual" field from the query:
SELECT ByPN_1.PartNumber, ByPN_1.LostPerSetup, ByPN_1.FirstOfFeederSize, ByPN_1.ActualMachine, ByPN_1.PermQty, ByPN_1.Leaf1, ByPN_1.FirstOfType, ByPN_1.NonPerm, IIf([nonperm]*[concurrentsetups]<1,1,CLng([nonperm]*[concurrentsetups])) AS QtyIfDed, [nonperm]*[setupsperday] AS MaxLoadsSavedPerDay, [qtyifded]*[setupsperday]/[concurrentsetups] AS DedLoadsSavedPerDay, IIf([maxloadssavedperday]<[dedloadssavedperday],[maxloadssavedperday],[dedloadssavedperday]) AS LoadsSavedPerDay, [loadssavedperday]*[laborrate]*[loadunloadperfeeder]*250/60 AS Labor_Annual, master_attr.STD_COST
FROM (ByPN_1 LEFT JOIN FeederCost1 ON (ByPN_1.ActualMachine = FeederCost1.Machine) AND (ByPN_1.FirstOfFeederSize = FeederCost1.Size) AND (ByPN_1.FirstOfType = FeederCost1.Type)) LEFT JOIN master_attr ON ByPN_1.PartNumber = master_attr.ITEM
WHERE (((ByPN_1.PartNumber)=107573));

Now the query returns what I expect:
PartNumberLostPerSetupFirstOfFeederSize
107573 3 12X4