Could my stored procedure be the cause of performance problems?

I have 3 major stored procedures, meaning they are the backbone of my application. I built them to be as dynamic as possible, but every 1st of the month the database crashes and our database people blame these 3 stored procedures.  The only reason I think they blame them is because they are ran so often they are running at the time the datbase crashes.  These stored procedures run about 10,000 times a day.

Here is an example of 1 of the stored procedures.  

The stored procedures work flawlessly the whole month running 10,000 times a day, but each 1st of the month the database crashes.

The fix for the database crash is to run:          sp_updateStats

Is my stored procedure to blame, if so then why doesn't it crash on other days instead of the 1st of the month.  Like clockwork the 1st of the month the database crashes.

Or is something else going on?  

DECLARE @TEIR int
SET @TEIR = 0

--temp table
CREATE TABLE #TempA(
..........
 )

Select @TEIR = ROLEID FROM UserInfo WHERE UserID = @WHO_WHERE;

Insert into #TempA(...............)
SELECT   ................
FROM(
	Select ..........
	From Work tt Left Join
		Error tf on tf.UserID=tt.UserID and tf.SubmitDate=tt.TimeDate
	Union All
	select .............
	from Error tf Left Join
		Work tt on tf.UserID=tt.UserID and tf.SubmitDate=tt.TimeDate
	where tt.UserID is null)  BF
Inner Join EmployeeManagement_History A on A.UserID=BF.UserID and BF.TimeDate between A.StartDate and isnull(A.EndDate,GetDate())
Where CASE @TEIR
	WHEN 1 THEN [Employee]
	WHEN 2 THEN [Supervisor]
	WHEN 3 THEN [Manager]
	END = @WHO_WHERE
AND BF.TimeDate between @StartDate and @EndDate
OPTION(MAXDOP 1);


-- Moved all the calculations down to here, so speed up the process
Select Distinct .............
from #TempA A LEFT JOIN  (
		SELECT 
		B.TimeDate,B.WorkDescription,
		UnitWorkedCummulative = ( SELECT sum(UnitWorked) 
									FROM #TempA A 
									WHERE A.TimeDate <= B.TimeDate
									 AND A.WorkDescription = B.WorkDescription),
		ErrorCummulative = ( SELECT sum(TotalErrors) 
								FROM #TempA C 
								WHERE C.TimeDate <= B.TimeDate
								AND C.WorkDescription = B.WorkDescription)
		FROM #TempA B	) B ON (A.TimeDate =B.TimeDate AND A.WorkDescription = B.WorkDescription  )
WHERE A.Work is not null
Order by A.WorkDescription, A.TimeDate
OPTION(MAXDOP 1);

Drop Table #TempA;

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