Query help: two sets of transaction groups, two sets of naming conventions, two cases in where clause

That usually means your script is supplying more parameters than there are question marks.

I GOT IT!

except five machines have had no rejects or production

So for now their yyyy-mmm column is null, and I am coalescing that

coalesce(sub1.Year_Month,FORMAT(DATEFROMPARTS(2022, 1, 1), 'yyyy-MMM'))
coalesce(sub1.Year_Month,sub2.Year_Month)
resolved my code similar to:

select coalesce(sub1.Year_Month,sub2.Year_Month) as Year_Month, coalesce( sub2.Line,sub1.Line) as Line, coalesce(sub1.Rejects,0) as Rejects,coalesce(sub2.highInfeed,0)-coalesce(sub2.lowInfeed,0) as Attempted, coalesce(sub2.highOutfeed,0)-coalesce(sub2.lowOutfeed,0) as Palletized
from (
select  min(t_stamp) as earliest, FORMAT(t_stamp, 'yyyy-MMM') as Year_Month, coalesce(sum(Quantity),0) as Rejects, LineNames.dashSpaceLine as Line,
min(infeed) as lowInfeed, max(infeed) as highInfeed, min(outfeed) as lowOutfeed, max(outfeed) as highOutfeed
from  Events 
Inner Join LineNames on LineNames.Machine=Events.Machine
where (t_stamp>DATEADD(month, -6,EOMONTH( GETDATE()))) and (Code>1100) and (:code=0 or :code=Code ) and Quantity is not null and ( :machine=-1 or 
		LineNames.Line=Case 	when :machine=1 then 'K-2' 
							  	When :machine=2 then 'K-3'
							  	When :machine=3 then 'K-4'
							  	When :machine=4 then 'K-5'
							  	When :machine=5 then 'K-6'
							  	When :machine=6 then 'K-7'
							  	When :machine=7 then 'K-8'
							  	When :machine=8 then 'L-9'
							  	When :machine=11 then 'K-12'
							  	When :machine=12 then 'L-13'
							  	When :machine=13 then 'K-14'
							  	When :machine=14 then 'K-15'
							  	When :machine=15 then 'A-16'
							  	When :machine=16 then 'A-17'
							  	When :machine=17 then 'L-18'
							  	When :machine=18 then 't 1 A'
							  	When :machine=19 then 't 3 A'
							  	When :machine=20 then 't 4 A'
							  	When :machine=21 then 't 1 B'
							  	When :machine=22 then 't 3 B'
							  	When :machine=23 then 't 4 B'
							  	else null end 
		 )
group by  FORMAT(t_stamp, 'yyyy-MMM'),LineNames.dashSpaceline
) sub1
Full Join 
(
select  min(t_stamp) as earliest, FORMAT(t_stamp, 'yyyy-MMM') as Year_Month, LineNames.dashSpaceLine as Line,
min(infeed) as lowInfeed, max(infeed) as highInfeed, min(outfeed) as lowOutfeed, max(outfeed) as highOutfeed
from  Events 
left Join LineNames on LineNames.noDashLine=Events.Line
where (t_stamp>DATEADD(month, -6,EOMONTH( GETDATE()))) and (Code>1100) and (:code=0 or :code=Code ) and infeed is not null and ( :machine=-1 or 
		Events.Line=Case 	when :machine=1 then 'K2' 
						  	When :machine=2 then 'K3'
						  	When :machine=3 then 'K4'
						  	When :machine=4 then 'K5'
						  	When :machine=5 then 'K6'
						  	When :machine=6 then 'K7'
						  	When :machine=7 then 'K8'
						  	When :machine=8 then 'L9'
						  	When :machine=11 then 'K12'
						  	When :machine=12 then 'L13'
						  	When :machine=13 then 'K14'
						  	When :machine=14 then 'K15'
						  	When :machine=15 then 'A16'
						  	When :machine=16 then 'A17'
						  	When :machine=17 then 'L18'
						  	When :machine=18 then 't1'
						  	When :machine=19 then 't3'
						  	When :machine=20 then 't4' 
		else null end )
group by  FORMAT(t_stamp, 'yyyy-MMM'),Events.Line,LineNames.dashSpaceline
) sub2
on sub2.Year_Month=sub1.Year_Month and sub1.Line=sub2.Line

order by coalesce( sub2.Line,sub1.Line) asc, coalesce(sub1.earliest,sub2.earliest) desc

I was throwing errors when I had used some comments earlier.
I said like
/* stuff */
and it threw errors like something index 40 out of range

edited in changes to the order by and coalescing in a few more cases between the two subqueries